object based access

Hi

I am working on a kind of big enterprise application 

now my requirement is this i want to configure access level permissions on each item of my entier application.

for example :

i am using membership for handling user.

my system have one user module .

so i want to configure permision some thing like this.

administrator can exexute all functions like createuser,edituser,deleteuser,viewuser etc.

semiadmin can just view user

here administrator and semiadmin is role ofsystem

but i have 2 user in semi admin role so all semi admin have bydefaul permision of viewing user but i want to give edit permision to one of them.

so how can i manage it is there any ready made librery like in .net which can manage it ewsily

or any suggestion are heartly wel come