...control mIRC with DDE?

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;