Hardware-wise, you will need something to read the temperature and get it into Labview, and a digital output to drive a relay to turn the fan on or off.
Your description of the control is a little confusing. You say you want to turn the fan on at 80 and off 65. But also say you want to stablize the room temperature at 72. A fan control really won't change the temperature of the room, it will just circulate the air around, it really won't make things cooler or warmer, unless the circulation is bring in air from a source that is less than the temperature you want to achieve. And and On-off control scheme will just have the temperature bounce between 80 and 65, it won't be able to stabilize it had 72, unless you tighten up the control range, and the circulation of air actually does affect the temperature.
All that said, going back to your original on/off scheme is doable in software. You will just need a loop that tracks the state of the digital output using a shift register. Also a case structure. Case 1, fan is off and temp >80, turn on fan, feed true value to right side shift register. Case 2, fan is on and temp< 65, turn off fan and feed false value to right side of shift register. Case 3, the default case when neither condition 1 nor 2 is true, do nothing just feed the wire through from the left to right side shift register.
