Aged Account Receivable

I am looking at the NAV_2009_SP1 Aged Accounts Receivable report. How can i create a field on the report to show the average amount of time it takes a customer to pay their closed invoices. I understand that this will be in the Cust_ Ledg_ Entry table and i will need to find out what entry number closed the invoice and snag this posting date? what would be the best way to add this field to the report?

have you seen closed by entry no field in cust ledger entry table?

You can use difference of receipt posting date & due date of invoice for calculation for average amount of time with what amol suggested.