How to clear transmission codes?

I have a 98 cherokee and I am wondering if anyone knows how to clear transmission codes. I can clear the regular check engine codes, but I can't clear the transmission codes. No I don't have a scanner of my own and autozone will no longer clear codes. I'd like to do it myself instead of having to pay for someone to push a couple buttons. I'm pretty sure I fixed the problem that was giving me the codes in the first place and I want to clear the codes so that I can check to see if I did indeed fix the problem.

Are you sure the cods don't clear themselves if the cause has been fixed.

I thought they did.