Custom Record Picker Report

We have the following relationships.

1. Contracts have many Invoices which have many Invoice Lines. [Invoice - Contract Number] is carried down to the invoice line record.
2. Contracts have many Payments which have many Invoice Lines. [Payments - Contract Number] is carried down the invoice line record.

We are matching invoice lines with payment lines.

We are trying to create a custom record picker report in the Payments Table that show, on the Invoice Line record, only those payments where [Invoice-Contract Number] = [Payments - Contract Number], i.e only show payments belonging to the Contract where the invoice is being applied.

However we can't get a filter working correctly where [Payments-Contract Number] is equal to [Invoice - Contract Number] in the record picker report.

Thanks for any assistance.

------------------------------
Tim Egerton
------------------------------