I re-entered the formula:
=iif(([txtQty]=0,"",Round((([txtMiles1]/[txtAvgMPH1])+[txtCount1],2))*[txtTruckHrRate])*[txtProfit%])
Saved it.
Opened the form (no errors)
Entered 1 in [txtCount1] and entered 1 is Zone1 and as soon as I clicked away from the field, the error "MS Access has stopped...