activate or deactivate buttons or menu-items

[Konstantinos Diplas <kdiplas Physik Uni-Bielefeld DE>]

Hi Folks,


 (i hope that my english is good enough)

 i've got the following question(s):
 a) how can i set a menu-item in a menu list to be active or not?
 b) is similar to (a). how can i do this with buttons as well?

 
 Thank You ... and greetings from germany


Ciao Kosta


 email:kdiplas physik uni-bielefeld de