Aannubis

Okay, I've browsed through the availabe UI downloadables and have also run through various areas of the forums but haven't been able to find the answer to my question, so here it is. I'm okay with the default UI except for one area. I keep hearing everyone talking about how much percent-per-kill experience they're getting and I'd like to add that function to the default UI. Is it possible to just toss in a percentage value to the regular and aa experience bars in the default UI or is it a lost cause?