Inject my Dll from a Service

[randy_dom]

Hi ,i've these Functions declared in my Dll , i'm focusing on
StartHook and StopHook , if i use them in a standalone Application all goes well .
But the problem is when using them in a Service i don't get any result there's no Hook .

Delphi-Quellcode:

function HookProc(code: Integer; wParam: WPARAM; lParam: LPARAM): LRESULT; stdcall;
begin
  Result := CallNextHookEx(Code, code, wParam, lParam)
end;
procedure StartHook; stdcall;
begin
  HookHandle := SetWindowsHookEx(WH_GETMESSAGE, HookProc, hInstance, 0);
end;

procedure StopHook; stdcall;
begin
  UnhookWindowsHookEx(HookHandle);
end;

The issue is only with Vista and up .