Also ich würd es so machen: (ungetestet)
Delphi-Quellcode:
var i : integer;
begin
for i := 1 to length(Edit1.Text) do
if ord(Edit1.text[i]) = 97
then Edit2.Text := Edit2.Text + 'z'
else if ord(Edit1.text[i]) = 65
then Edit2.Text := Edit2.Text + 'Z'
else Edit2.Text := Edit2.Text + Char(Ord(Edit1.text[i])-1);