function CustomMsg(const DlgCaption,Text:string; MsgType:TMsgDlgType; Buttons:TMsgDlgButtons):integer;
var
  MsgBox   : TForm;
  i        : byte;
  PicWidth : integer;
begin
  MsgBox := CreateMessageDialog(Text,MsgType,Buttons);
  try
    //Change TEXT Properties
    with (MsgBox.Controls[1] as Tlabel) do
    begin
      Font.Name := "Tahoma";
      Font.Style := Font.Style + [fsBOLD];
      Font.Size := 8;
      WordWrap := False;
    end;
    //Change Messagebox Properties
    with MsgBox do
    begin
//      BiDiMode := bdRightToLeft;
      Font.Name := "Tahoma";
      Font.Size := 8;
      Caption := DlgCaption;
      Width := (Controls[0] as TImage).Width +
               (Controls[1] as Tlabel).Width + 100;
    end;
  //Change Buttons" caption
    for i := 0 to MsgBox.ControlCount-1 do
      if (MsgBox.Controls[i] is TButton) then
        with (MsgBox.Controls[i] as TButton) do
        begin
          if      (UpperCase(Caption) = "&OK")         then Caption := "EC??I"
          else if (UpperCase(Caption) = "&YES")        then Caption := "E??"
          else if (UpperCase(Caption) = "&NO")         then Caption := "I??"
          else if (UpperCase(Caption) = "CANCEL")      then Caption := "C???C?"
          else if (UpperCase(Caption) = "&ABORT")      then Caption := "?U?"
          else if (UpperCase(Caption) = "&RETRY")      then Caption := "I?EC??"
          else if (UpperCase(Caption) = "&IGNORE")     then Caption := "?I"
          else if (UpperCase(Caption) = "&ALL")        then Caption := "???"
          else if (UpperCase(Caption) = "N&O TO ALL")  then Caption := "I?? E? ???"
          else if (UpperCase(Caption) = "YES TO &ALL") then Caption := "E?? E? ???"
          else Caption := "?C???C";
        end; {with}
    Result := MsgBox.ShowModal;
  finally
    MsgBox.Free;
  end; {try}
end;

مثال:

procedure TForm1.Button1Click(Sender: T);
begin
 CustomMsg("caption","this is a test for delphi center",mtWarning,mbOKCancel)
end;