Multiple Category Permalink Selection?

Hey guys….. Ok, lately I’ve posted a couple articles that I have put in multiple categories, however it relates to one category more than the other…. WP just decides to just use the first category on the list to shove in the URL for the permalink… I’m finding this very annoying as I want it to use the category name in the permalink that it is most related to, for SEO purposes… I’ve even tried just selecting the main category for it to create the permalink with the correct category, it does, but then when you add other categories it changes it to the first category again!!!

So was wondering if anything exists that can help me!?

Thanks!