Your the experts.. Please help! :)

Right.. What I am trying to achieve I am not sure can be done..

I want to have a separate wordpress theme for my facebook iframe... My facebook page users will be able to use sections of my site via facebook and post ads via the facebook iframe.. The problem is obviously my site template is too large to fit in the iframe.. I need to find out how to implement a different theme for the facebook iframe..

Can anyone give me any pointers?

Kindest Regards,