Unfortunately the way you asked your question has lended itself to people giving you a different answer than I think you were seeking. It seems you are asking about the purpose of the UVB bulb, not about what temperature your basking bulb should be, although it seems some of the responses have been about the latter.
The purpose of the UVB bulb is not to elevate the body temperature. The UVB bulb is important because the UVB rays are important for calcium metabolism pathways, particularly as they effect vitamin D3 production.
Here are a few articles you should read regarding lighting for chameleons:
http://www.chameleonnews.com/04AugBeveridge.html
http://www.chameleonnews.com/10JulWeldon.html
http://www.uvguide.co.uk/intro.htm
Also, exactly what type of R-Zilla UVB bulb do you have? Some have been connected to blindness issues so its important to make sure you do not have one of these bulbs.
Chris