Code execution in CI Clas Definition

[Basia]

is it possible to execute code in the Class Definitions of Items in CMDB?

i would like to implement a counter, that starts on a user defined value, and is decremented each time a link is made to that item.

also, is each item of a class definition it's own instance in relation to the scope of variables?

location of Item definition:
Config Item Management -> Change Class Definitions