CALCFIELDS using DateFilter in report

colingbradley

I have created a flowfield that uses a Date Filter:
Sum("Job Ledger Entry"."Remaining Amount" WHERE (Global Dimension 2 Code=FIELD(Code),Open=CONST(Yes),Chargeable=CONST(Yes),Posting Date=FIELD(Date Filter)))

I need to check the total remaining amount for the date selection from the Sales Invoice/Get Job Usage report.
Is there a way to CALCFIELDS(flowfield) and use the date selection?

Usage.
If the user wants to get open entries for Posting Dates ..31/01/10 and the total remaining amount does not exceed the contract amount remaining then allow but if greater, then ERROR.

The only other way I can see is to find the total by varJobLedEntry.setfilter etc and use the date selection as a filter and total the remaining amount. The calcfields option is just so much neater if I can use it.