Unfortunately you'll have a hard time getting an accurate temperature relative to the thermistor that's inserted into the heat block. The surface of the heaterblock is quite a bit cooler than the internal thermistor location.

You could always try buying your own thermistor and measuring it's resistance and then doing the conversion on your own.

http://www.mouser.com/ProductDetail/...2FPgvFdg%3D%3D
http://www.atcsemitec.co.uk/gt-2-glass-thermistors.html