Getting dynamic stylesheet to work in Advnaced Guestbook

Hello, I'm trying to skin the advanced guestbook with custom stylesheets that the user can choose from, the problem is that when I add the link to the head template the guestbook doesn't parse the php script to check my cookie for correct stylesheet to use. Any ideas on how to get the php to pars? I have it working on all my other pages but the guestbook, any help is most appreciated.