I was going to ask how can I now if the program is already been executed,
but Ive already seen the anwser. My problem now is that my program needs
to check if the Program is running, and if it is, make this existing
instance of the program to open the file that was assigned to the first.
How can I give an order to the program from outside it?

You can find if your program is already running using FindWindow. To 'order' him to open the file, you can use the WM_COPYDATA message:

Put this in your project source:

var     Prev:HWND;
        pCopyData: TCopyDataStruct;
        FileToLoad: String;

    Prev := FindWindow('TForm1', nil); //your main form class
        if ((Prev <> 0) then
        begin
        for i:=1 to ParamCount do
           begin
                if FileExists(ParamStr(i)) then
                begin
                        FileToLoad := AnsiLowerCaseFileName(ParamStr(i));
                        with pCopyData do
                        begin
                                dwData := 0;
                                cbData := Length(FileToLoad) + 1;
                                lpData := PChar(FileToLoad);
                                end;
                                SendMessage(Prev, WM_COPYDATA, Application.Handle, Longint(@pCopyData));
                end;
        end;
        SetForegroundWindow(Prev);
        Halt(1);

        //
        Application.Initialize;
        //.....
  end;

in your main form unit:

type Form1=class(TForm)
        ...
        private;
                procedure OpenFromAnother(var Message: TMessage);message WM_COPYDATA;
end;

procedure TForm1.OpenFromAnother(var Message: TMessage);
var TheFileName: String;
  pCopyData: PCopyDataStruct;
begin
   pCopyData := Pointer(Message.LParam);
   TheFileName := AnsiLowerCaseFileName(String(PChar(pCopyData^.lpData)));
   OpenFile(TheFileName);
end;

NOTE! if you run your program within Delphi IDE, it will never execute since there is already a TForm1 window (the designer). Compile it and execute it outside the IDE.

HTH, Alex.

Mrlon M. Brum <naoresponda@por_email.com> wrote in article <01be80f2$07272740$9b2aa...@SERVIDOR.NESS.NET>...