Query - Selection Option on Subtotal

A customer has created a query and interface using transactions SQ01 and SQ02 that generates a report from tables EKKO - Purchase Document Header and EKPO - Purchase Document Item.

Referencing the Net Order Amount (EKPO-NETWR) they wanted subtotals to appear by Purchasing Document Number. I was able to give them that by changing the Sort and Total check boxes in their original query. So now they currently have a report that lists the Purchase Order Document (EKPO-EBELN), each Item Number for the Purchase Order (EKPO-EBELP), the Net Order Value for each item (EKPO-NETWR), as well as query-generated subtotals for each Purchase Order and a grand total of all Purchase Orders.

Now the customer would like to be able to select on the query-generated subtotals. For example, select all Purchase Order Documents whose query-generated subtotal is greater than $5,000, or select all Purcahse Order Documents whose query-generated subtotal is equal to $1,000.

Any suggestions on how to accomplish that would be greatly appreciated. Thank you.