How to do redirects

Hi,

I need a little help with this one. Here is the thing.

I have three sites and all of them use the boost module.

One of these sites acts as a global site and it redirects the user to either of the other two sites if the user meets some criteria.

Right I do this using javascript/ajax to determine if the user needs to be redirected but the problem is the user get to see the global site before the redirect.

Do you suggest something for this? I could prevent boost to cache the homepage but I loose a lot from speed perspective.

Thank you