Delphi Anfänger findest fehler nicht: error in prozedur

[eDonkey]

Hallo Community, ich bin gerade dabei delphi zu lernen und programmiere nun einen taschenrechner der auch mit hotkeys arbeitet.

bei meiner backspace prozedur bekomm ich aber den error:
[Error] Rechner.dpr(307): Incompatible types: 'String' and 'procedure, untyped pointer or untyped parameter'
Zeile hab ich markiert, ist in der vorletzten prozedur.
könnt ihr mir weiterhelfen? schonmal danke im vorraus

hier der sourcecode:

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Delphi-Quellcode:

unit Rechner;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, StrUtils;

type
  TForm1 = class(TForm)
    LabelZeichen: TLabel;
    Edit: TEdit;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    Button6: TButton;
    Button7: TButton;
    Button8: TButton;
    Button9: TButton;
    Button10: TButton;
    Button11: TButton;
    Button12: TButton;
    Button13: TButton;
    Button14: TButton;
    Button15: TButton;
    Button16: TButton;
    Button17: TButton;
    Button18: TButton;
    Button19: TButton;
    Button20: TButton;
    Button21: TButton;
    Button22: TButton;
    Button23: TButton;
    LabelMemory: TLabel;
    EditErgebnis: TEdit;
    procedure Button9Click(Sender: TObject);
    procedure Button19Click(Sender: TObject);
    procedure Button20Click(Sender: TObject);
    procedure Button22Click(Sender: TObject);
    procedure Button10Click(Sender: TObject);
    procedure Button13Click(Sender: TObject);
    procedure Button14Click(Sender: TObject);
    procedure Button6Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
    procedure Button18Click(Sender: TObject);
    procedure Button16Click(Sender: TObject);
    procedure Button11Click(Sender: TObject);
    procedure Button21Click(Sender: TObject);
    procedure Button23Click(Sender: TObject);
    procedure Button17Click(Sender: TObject);
    procedure Button12Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button7Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button15Click(Sender: TObject);
    procedure Button8Click(Sender: TObject);
    procedure Backspace;
    procedure FormKeyDown(Sender: TObject; var Key: Word;
      Shift: TShiftState);


  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  Safemode: Boolean = false;
  Memory: String = '';

implementation

{$R *.dfm}

procedure TForm1.Button9Click(Sender: TObject);
begin
If Edit.Text <> '0' then
  Edit.Text := Edit.Text + '0';
end;

procedure TForm1.Button19Click(Sender: TObject);
begin
If Edit.Text = '0' then
  Edit.Text := '1'
else
  Edit.Text := Edit.Text + '1';
end;

procedure TForm1.Button20Click(Sender: TObject);
begin
If Edit.Text = '0' then
  Edit.Text := '2'
else
  Edit.Text := Edit.Text + '2';
end;

procedure TForm1.Button22Click(Sender: TObject);
begin
If Edit.Text = '0' then
  Edit.Text := '3'
else
  Edit.Text := Edit.Text + '3';
end;

procedure TForm1.Button10Click(Sender: TObject);
begin
If Edit.Text = '0' then
  Edit.Text := '4'
else
  Edit.Text := Edit.Text + '4';
end;

procedure TForm1.Button13Click(Sender: TObject);
begin
If Edit.Text = '0' then
  Edit.Text := '5'
else
  Edit.Text := Edit.Text + '5';
end;

procedure TForm1.Button14Click(Sender: TObject);
begin
If Edit.Text = '0' then
  Edit.Text := '6'
else
  Edit.Text := Edit.Text + '6';
end;

procedure TForm1.Button6Click(Sender: TObject);
begin
If Edit.Text = '0' then
  Edit.Text := '7'
else
  Edit.Text := Edit.Text + '7';
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
If Edit.Text = '0' then
  Edit.Text := '8'
else
  Edit.Text := Edit.Text + '8';
end;

procedure TForm1.Button5Click(Sender: TObject);
begin
If Edit.Text = '0' then
  Edit.Text := '9'
else
  Edit.Text := Edit.Text + '9';
end;

procedure TForm1.Button18Click(Sender: TObject);
begin
If not Safemode then
  EditErgebnis.Text := FloatToStr(StrToFloat(Edit.Text));
If not Safemode then
  Edit.Text := '0';
  Safemode := true;
  LabelZeichen.Caption := '+';
end;

procedure TForm1.Button16Click(Sender: TObject);
begin
if not AnsiContainsText(Edit.Text,',') then
  Edit.Text:= Edit.Text+',';
end;

procedure TForm1.Button11Click(Sender: TObject);
begin
EditErgebnis.Text := '';
LabelZeichen.Caption := '';
Edit.Text := '0';
Safemode := false;
end;

procedure TForm1.Button21Click(Sender: TObject);
begin
Edit.Text := '0';
end;

procedure TForm1.Button23Click(Sender: TObject);
begin
If not Safemode then
  EditErgebnis.Text := FloatToStr(StrToFloat(Edit.Text));
If not Safemode then
  Edit.Text := '0';
Safemode := true;
LabelZeichen.Caption := '-';
end;

procedure TForm1.Button17Click(Sender: TObject);
begin
If not Safemode then
  EditErgebnis.Text := FloatToStr(StrToFloat(Edit.Text));
If not Safemode then
  Edit.Text := '0';
Safemode := true;
LabelZeichen.Caption := '*';
end;

procedure TForm1.Button12Click(Sender: TObject);
begin
If not Safemode then
  EditErgebnis.Text := FloatToStr(StrToFloat(Edit.Text));
If not Safemode then
  Edit.Text := '0';
Safemode := true;
LabelZeichen.Caption := '/';
end;

procedure TForm1.Button4Click(Sender: TObject);
var
s : String;
begin
s := Edit.Text;
If s = '0' then
else if AnsiContainsText(s, '-') then
  Delete(s,1,1)
else
  s := '-' + s;
  Edit.Text := s;
end;

procedure TForm1.Button7Click(Sender: TObject);
begin
Memory := Edit.Text;
LabelMemory.Caption := 'M'
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
If Memory <> '' then
   Edit.Text := Memory;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
Memory := '';
LabelMemory.Caption := '';
end;

procedure TForm1.Button15Click(Sender: TObject);
var
Wert1,Wert2: Extended;
Casevar: Integer;
Ergebnis: String;
begin
Casevar := 0; //compiler meckern umgehen
If (EditErgebnis.Text <> '') and (EditErgebnis.Text <> 'error') then begin
  Wert1 := StrToFloat(EditErgebnis.Text);
  Wert2 := StrToFloat(Edit.Text);
  If LabelZeichen.caption = '+' then
    Casevar := 1
  else If LabelZeichen.caption = '-' then
    Casevar := 2
  else If LabelZeichen.caption = '*' then
    Casevar := 3
  else If LabelZeichen.caption = '/' then
    Casevar := 4
  else If (LabelZeichen.caption = '/') and (Edit.Text = '0') then
    Casevar := 5;
  If (Casevar = 1) xor (Casevar = 2) xor (Casevar = 3) xor (Casevar = 4) xor
     (Casevar = 5) then begin
    Case Casevar of
      1: Ergebnis := FloatToStr(Wert1 + Wert2);
      2: Ergebnis := FloatToStr(Wert1 - Wert2);
      3: Ergebnis := FloatToStr(Wert1 * Wert2);
      4: Ergebnis := FloatToStr(Wert1 / Wert2);
      5: Ergebnis := '0';
    end;
  end
end;
EditErgebnis.Text := Ergebnis;
end;

procedure TForm1.Button8Click(Sender: TObject);
var
s: String;
begin
s := Edit.Text;
If (s <> '0') and (s <> '1') then begin
  if AnsiContainsText(s, '-') then begin
    Delete(s,1,1);
    Edit.Text := FloatToStr(Sqrt(StrToFloat(s)));
  end;
  if s = '1,00000000000001' then
    Edit.Text := '1'
  else
    Edit.Text := FloatToStr(Sqrt(StrToFloat(s)));
end;
end;

//Problemprozedur
procedure TForm1.Backspace;
var
Str: String;
begin
Str := Edit.Text;
If Length(Str) < 1 then
  Edit.Text := Delete(Str, Length(Str), 1)
else  // line 307...
  Edit.Text := '0';
end;

procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
  case Key of
    VK_NUMPAD0, $30 : Button9.Click;
    VK_NUMPAD1, $31 : Button19.Click;
    VK_NUMPAD2, $32 : Button20.Click;
    VK_NUMPAD3, $33 : Button22.Click;
    VK_NUMPAD4, $34 : Button10.Click;
    VK_NUMPAD5, $35 : Button13.Click;
    VK_NUMPAD6, $36 : Button14.Click;
    VK_NUMPAD7, $37 : Button6.Click;
    VK_NUMPAD8, $38 : Button3.Click;
    VK_NUMPAD9, $39 : Button5.Click;
    110 : Button16.Click;
    106 : Button17.Click;
    107 : Button18.Click;
    109 : Button23.Click;
    111 : Button12.Click;
    VK_RETURN : Button15.Click;
    VK_BACK : Backspace;
    VK_ESCAPE : close;
  end;
end;

end.

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