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

uses
   DdeMan;

 procedure mIRCDDE(Service, Topic, Cmd: string);
 var
   DDE: TDDEClientConv;
 begin
   try
     DDE := TDDEClientConv.Create(nil);
     DDE.SetLink(Service, Topic);
     DDE.OpenLink;
     DDE.PokeData(Topic, PChar(Cmd));
   finally
     DDE.Free;
   end;
 end;

 procedure TForm1.Button1Click(Sender: TObject);
 begin
   mIRCDDE('mIRC', 'COMMAND', '/say Hallo von SwissDelphiCenter.ch');
 end;