Interest Calculation based on multiple column

jake_callabp

I am attempting to calculate interest based on a past due value in one of 4 columns. I need this formula to calculate all 4 columns because the amount may appear in one column this week and move to another the following week. I am able to get it to calculate using one column but when i attempt to add more columns i get an invalid operation. Maybe it would be easier to do this based on a date?

I am fairly new to Smartsheet and formulas so any help would be greatly appreciated.

Hollie Green

=Sum([Thirty one]@row:[One Twenty One]@row)*0.015