Load Random swfs - with control. Sound stupid?

Here is what I need to do. I need to load 3 random movies into a main movie. However, I need to be able to control the randomness of the loading content. The client wants one movie to appear 50% or the time and the other two to appear 25% of the time. Make sense?

I read the random movies tutorial but I was not sure how to adjust it to include a controled random event.

Tom