Create Filter For Calculation in Report

Hi, We just moved to NAV 2015 and I've been using the Report Builder to create reports. It's working very well. I recently created a report that has three columns Qtyonhand and QtyonOrder which come from the Item card - then in the third is an expression that subtracts QtyOnOrder from QtyonHand to show QtyShort. Our users want to run the report two ways - one with all rows and then with only the rows with the QtyShort >0. Is this possible? If so, do I add it as a parameter in Report Builder or option/request page? Then how do I pass that to the report so the expression to hide =IIF(SUM(Fields!ID.Value,"YourGroupName")>=1,True,False) runs? Maybe there is a better way? We have this in a PowerPivot report with two sheets one for all and one for the short only and on print, it prints both sheets, but management wanted it in NAV. I've got the first part done, but stuck on the second part.
Thanks for the help.