Load from cache when available

Let me start by saying I’m not sure if this is the right place to post this question.

I created a flash header for a site and although it is fairly small, it is on every page and I think it is downloading it once for every page. They have exceeded their bandwidth alotment last month and I want to know how I can tell if this is the cause or not.

How do you code it to read it from the users cache if it has been downloaded already?