problem with enable and disable menus

Question

Hi,
I am creating a c# windows application with 2 forms. First form has a menu and some menu items. If any meny item is disabled, what can be done, so it is enabled from the second form.
E.g. Second form is for login, and when a user logs correctly, to be able to use the menus from the first form.
Thanks,
Trifon.