Add negative amounts to out-of-pocket formula

[K_CPA]

You should be able to add a negative amount in to the out-of-pocket formula. 

Currently ITA is calculating the "cost" of doing a cost seg as the amount of depreciation my client is savings. This is inaccurate as the cost is the fee to a specialist to perform the study. I would like to be able to back out ITA's default amount (the depreciation) and add in the specialist fee.