Calculations using two sensor values in Digi-Key IoT Studio

Using DigiKey iOT Studio, I am trying to calculate the Heat Index, which is a function of temperature and relative humidity [HI = f(T, RH)]. I can easily read the temperature and relative humidity from a BME680 element and send those values to their respective BLECharacterisitc elements. But I can’t figure out a way to do a calculation with the values from the two sensors (i.e., temperature and relative humidity). It seems like I can do most anything with temperature and humidity separately, but not together.
Any advice would be appreciated.
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Thanks,
Ken