Cfm fan question

How can i make my CFM exhaust fan to turn on when it hits a certain temperature and cool the room down then turn off once it gets back down to the right temp?? its a standard outlet plug and the cfm is pumping the hot air into my attic.
on a budget too.

Lux win 100. In cooling mode, program in your ideal temp and the fan will run when it is any warmer than that and then auto shut off when it gets back to ideal. $35
http://www.amazon.com/Lux-Heating-Cooling-Programmable-Thermostat/dp/B000E7NYY8/ref=sr_1_1?ie=UTF8&qid=1357458185&sr=8-1&keywords=temperature+controller

Although it's more money, you might want to consider a Titan Controls Mercury 4. It's designed for the growing environment and won't shut your fan completely off. This will help with odor when in flower. Also the Temp 2V is the same unit. Idle control etc. They work well...I just ordered one.

Namaste