Open the Ports & pins Input Signals. Find the THC UP input, turn on Emulated (green check) and you can map any keyboard key to the input so striking that key will be the same as getting an UP signal from the THC circuit.
Do the same with the THC DOWN Signal (using another keybutton. I use U key for UP and D for Down.
Emulation substitutes a keystroke for a signal. I have used it a lot lately working on software (plug-ins) for rotary plasma cutting.