int _tmain(int argc, _TCHAR* argv[])
{

    CString dataToSend = _T("MY DATA");
    COPYDATASTRUCT cds;
    cds.dwData = 1; // can be anything
    cds.cbData = sizeof(TCHAR) * (_tcslen(dataToSend) + 1);
    cds.lpData = (void*)dataToSend.GetBuffer(cds.cbData);

    HWND hwndFound;         // This is what is returned to the caller.
    hwndFound = FindWindow(_T("TMyForm"), 0);


    if (hwndFound)
    {
        printf("WINDOW IS FOUND %i... Sending a message...n", hwndFound);
        SendMessage(hwndFound, WM_USER + 1, (WPARAM)hwndFound, (LPARAM)(LPVOID)&cds);
    }
    else
    {
        printf("WINDOW IS NOT FOUND!n");
    }



    char* end = "";
    printf("Press enter to continue...");
    scanf(end);

    return 0;
}

private
    procedure WMCopyData(var Msg : TWMCopyData); message WM_COPYDATA;
....


procedure TMyForm.WMCopyData(var Msg: TWMCopyData);
var
   s : AnsiString;
begin
   s := PAnsiChar(Msg.CopyDataStruct.lpData) ;
   ShowMessage(s);
end;

....

procedure TMyForm.MyButtonClick(Sender: TObject);
begin
   // Checking my handle
   ShowMessage(IntToStr(Handle));
end