User Rights System

I need some advice with a msSQL 2005 database

I'm creating a administration program in vb.net based on a new msSql db. This programme is involved with customeradmin, facturation, products, sales,...

by example: Some employees don't has anything to do with product, so they don't need the rights to delete, create or edit it.
The question is how can i resolve this problem, because i don't find any good solution. The rights are for every employee different, and can be changed by a admin panel. The admin can give a employee specific rights for every part of the programme


so how can we give a user certain rights when he is logging in into the program.



thanks, BoardD :S ;)