Need to total the sum of all vendor bill(s) amount for a PO

Hi,

This seems like a simple thing to do, however it is being very tricky. What we need is a saved search that totals the multiple bills for a PO.

CRITERIA:

Transaction Type: Purchase Order

Applying Transation: Type = is Bill

Main Line: is false

RESULTS:

Date

Transaction Number

Amount

Applying Transaction: Transaction Number

Applying Transaction: Amount

Created From

Formula (Currency) : {amount}-(SUM{applyingtransaction.amount})

For some reason this is not working and erroring out.

NOTE: To clarify, we are trying to find out if there is a difference between the total of Bills to the amount in PO.

Thanks in advance!!