Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

// Sender: Send data 
// Sender: Daten schicken 

procedure TForm1.Button1Click(Sender: TObject);
 var
   aCopyData: TCopyDataStruct;
   hTargetWnd: HWND;
 begin
   with aCopyData do
   begin
     dwData := 0;
     cbData := StrLen(PChar(Edit1.Text)) + 1;
     lpData := PChar(Edit1.Text)
   end;
   // Search window by the window title 
  // Fenster anhand des Titelzeilentext suchen 
  hTargetWnd := FindWindowEx(0, 0, nil, PChar('WM_COPYDATA-Receiver'));
   if hTargetWnd <> 0 then
     SendMessage(hTargetWnd, WM_COPYDATA, Longint(Handle), Longint(@aCopyData))
   else
     ShowMessage('No Recipient found!');
 end;


 (* -------------------------------------------------------------------- *)


 // Recipient - Receive data 
// Empfanger - Daten empfangen 

type
   TForm1 = class(TForm)
     private
     { Private declarations }
     procedure WMCopyData(var Msg: TWMCopyData); message WM_COPYDATA;
   public
     { Public declarations }
   end;

 procedure TForm1.WMCopyData(var Msg: TWMCopyData);
 var
   sText: array[0..99] of Char;
 begin
   // generate text from parameter 
  // anzuzeigenden Text aus den Parametern generieren 
  StrLCopy(sText, Msg.CopyDataStruct.lpData, Msg.CopyDataStruct.cbData);
   // write received text 
  // Empfangenen Text ausgeben 
  label1.Caption := sText;
 end;