ALV - Configuring totals for new columns??

I have made a copy of program RFUMSV00 into a Z program and added new columns in the ALV tables that are outputted (they are created dynamically).

When i go to run this program, you can click on "Output Lists" and click on "Configure" and you can choose to Sum the columns.

My new columns look like numbers (dollar amounts) as they should, but when you click on the sum button, i get the error "Desired operation cannot be performed for column".

This is a legal requirement needed asap, so any help is greatly appreciated!!!

THANK YOU!