How to convert a film to become exactly 6 mb?

I have a movie i want to upload to a blog, but it cant be bigger than 6mb. What is the fastest way to compress the movie to be exactly 6mb or a little smaller and keep the quality as good as possible? I have QuickTime Pro and Final Cut, is there a way to this with one of those apps? I’m ok with downloading apps if that’s what i need, but i’m not paying for anything :p