{....}
var
 WindowName: Integer;
 ProcessId: Integer;
 ThreadId: Integer;
 buf: PChar;
 HandleWindow: Integer;
 Write: Cardinal;
{....}
const
 WindowTitle = 'a program name';
 Address = $A662D6;
 PokeValue = $4A;
 NumberOfBytes = 2;
{....}

procedure TForm1.Button1Click(Sender: TObject);
begin
 WindowName := FindWindow(nil, WindowTitle);
 if WindowName = 0 then
 begin
  MessageDlg('Program not running.', mtWarning, [mbOK], 0);
 end;
 ThreadId := GetWindowThreadProcessId(WindowName, @ProcessId);
 HandleWindow := OpenProcess(PROCESS_ALL_ACCESS, False, ProcessId);
 GetMem(buf, 1);
 buf^ := Chr(PokeValue);
 WriteProcessMemory(HandleWindow, ptr(Address), buf, NumberOfBytes, Write);
 FreeMem(buf);
 CloseHandle(HandleWindow);
end;