opps, sorry, I should have mentioned this is the first time I have setup a form. I saw the other two options, but I was not sure how to use them. I understand your instructions.
So in my case, my field names are Total-Expense and Deductible-Expense.
So, in the Net-Expense field, I would use the Simple field notation and enter:
Total-Expense - Deductible-Expense
Ok, I will try that - thanks.