You are a genius if you can answer this one. How do I add the prior retainer balance to a bill cover sheet?

Sounds simple right? I dragged every possible database field over and none gives this balance. This number is available in a funds balance report so it doesn't make sense that I can't add it to a cover sheet.

Here is what I want on my cover sheet

Prior Retainer Balance Before Applying Current Charges

Less: Current Charges

Retainer Balance after Applying Current Charges

This is a simple cover sheet. Why can't I get it to work?

If you can answer this one, drinks are on me—seriously.