Generic dialog with custom captions for buttons

I know this issue have been up since before (ex. Best way to show customized message dialogs), but I still don't find what I want.

I started like this:

class function TAttracsForm.MessageDlg(const aMsg: string; aDlgType: TMsgDlgType; Buttons: TMsgDlgButtons; aCaptions: array of String; aDefault: TMsgDlgBtn): TModalResult;
var
  vDlg: TForm;
  i: Integer; 
begin
  if aButtons.Count = aCaptions.Count then
  begin
    vDlg := CreateMessageDialog(aMsg, aDlgType, Buttons);
    try
      for i := 0 aCaptions.Count - 1 do
        TButton(vDlg.FindComponent(Buttons[i].Caption)).Caption := aCaptions[i]; 

      vDlg.Position := poDefaultPosOnly;
      Result := vDlg.ShowModal;
    finally
      vDlg.Free;
    end;
  end;
end;

And the call would look like:

if (MessageDlg('Really quit application ?', mtWarning, 
       [mbNo, mbCancel, mbYes], {'No save', 'Cancel', 'Save'}) = mrYes) then

But the above code of course don't compile. I don't know how to get one item of an set in the loop and how to get the total count of it in the beginning.