### Title

Modify Sum Functions

### Post

I’m using Sum calculation functions (Item Total Qty, Item Total Amount, etc.) to total items from a portal. I need to manipulate these functions (adding or subtracting from other tables) but cannot modify a sum function.

How can this be accomplished?

That a look at the Invoice starter template. Two tables with invoice calculations Invoices and Invoice data. Invoice Data Contains a Discount Calculation, then there are Subtotal, and Total Calculations you may also want to take a look at.