https://community.kobotoolbox.org/t/advanced-calculate-function-using-if-statement/6350/3

We should be able to have if statments in Arithmetic Calculations. Ex: I have a Home Miles box that should be subtracted from Total Miles when the person went from Home to a location or went to Home from a location.

I know this can probably be done in Workflow but we really would like to calculate from the form itself.