Help with retrieving blogid....

Hello their,
I was working on new blog template lately..

I want to get the blogid for the template selected just after the signup process...

I am having a wpmu setup.
As the user selects the template in signup page ... I want to get that info (particularly the blogid of selected template)...and want to use it in my another custom plugin which creates a hook in the same page(i.e.signup.php)..

please guide me with these..Thx