Cerrar MDI y Application.MessageBox

[MaJeSTiC]

procedure TMainFormMDI.FormClose(Sender: TObject;
var Action: TCloseAction);
begin
if Application.MessageBox('Desea Continuar...',
'Esta a punto de cerrar xxx',mb_OkCancel+mb_IconExclamation)= IdOk
then
Action:=CaFree
else
Action:=CaNone;
end;



Gracias a todos...