different security level

hi

i want to know how to handle different security level with form authentication.
for example :
i have three security level:
Admin level(which access to all page)
user file(which access to som page)
guest level (which only access to a few page)
and i authenticate user with sql server and also there are some file that the content of them is depands on the level of user
for example the file member .aspx is use for all level but for each level the content is different to others.
plz help me how to do that?
thanx