If I were you I'd set up this from inside Access and not go about messing around in VB-code.
But then again, it can be done. Set a referense to ADOX and create a collection object to point to your DB. Then create a user object for the administration of user permissions.
I'm sorry if I'm a bit vague, but this is as yet only theory for me. It would be interesting to see your solution if you decide to continue, and I'd be happy to continue provide input.
Good Luck
-Mats Hulten