Active control of thermoelectric cooler?

Hi-

I'm trying to model a system where the power draw of the TEC is driven by a PID loop, such that the chip temperature is held constant.    Seems as though a goal dependent dependency would be just the thing-- the help files discuss using such a beast, but it's not clear whether this functionality is available for the TEC element in flow simulation. 

I've tried inputting an equation based on a SurfaceGoal, but it gets spit out as being "wrong number format"-- the syntax I tried is "=0.5+1.5 * (SG_1 - 293 )^2 / 40^2" , where SG_1 is a surface goal that shows up in the project tree.

Am I just messing up the syntax, or am I attempting the impossible? 

Thanks,

Michael

SolidworksFlow Simulation