This is very much possible beacon, to be honest I have found creating my own security system much easier than using asccess built in security.
However with that being you can use SQL to add users / permissions / groups etc.
You will need to simply tie the following sql procedures to execute within unbound forms.
To create an account sql is
CREATE USER user1 password1 pid1 [, user2 password2 pid2 [, etcetcetc] ]
to create a new group
CREATE GROUP group1 pid1 [, group2 pid2 [, etcetcetc] ]
To change a password you can use
ALTER USER user PASSWORD newpassword oldpassword
To add a user to a group you can use
ADD USER user1 [, user2 [, etcetcetc ]] TO group
To remove a user you can use
DROP USER user1 , [, user2 [, etcetcetc ]] FROM group
To add them a priveladge you can use
GRANT privilege1 [, privilege2 [, etcetcetc ] ] ON {TABLE table1 | OBJECT object1 | CONTAINER container1} TO account1 [, account2 [, etcetcetc]]
Where you select a priveledge clause within the {} brackets above
All of the above referenced from access 2002 desktop developers handbook chapter 5 incase you have it and want some more detail.