Hey Joey,
This stuff might do the trick. The company does claim the product repels wasps...
http://www.bugrepel.com/
According to the ad, your bats might even live a longer, happier life, enjoy the outdoors more AND smell better while doing it. Of course, if they get it on themselves those nightly forages might get a little tougher! If it doesn't work, I guess there's always the lighter fluid!
Seriously though, I suspect Keith is right. They probably get along just fine. I imagine they share habitats in barns, belfry's, under bridges etc.
I'm curious, are any bats currently using the box?
BL