incorporating multiple designs

[milkmycow]

ok, so i know on VB we can have it so that a user can change his/her style, and anytime they come back, that style will show up for them..

i want to incorporate this into my whole site. I have about 4 different designs i have made, and i want the user to be able to select the design of choice, and if they are a vb member, it will always display that design until they choose otherwise.

and then people who arent forum members will just get the default design.

each design would have its own forum style as well

any ideas on the best way 2 do this?