How can I add "payments made" and "current balance" to the superbill?

How can I add "payments made" and "current balance" to the superbill?

HI, I am creating invoices and printing out superbills that I then submit to my billing company (not charm) to be used to claim payments from insurance. 
I need a way to have the superbill template add payments made by patient and the current balance. For instance, a patient is seen in the office, he pays his copay of $20, I log the payment into charm. When I print out the superbill to send it to the billing company, who then claims the total amount from the insurance, I need a way to let the billing company know, if the copay has already been paid and what the current balance is, so these sums are not again billed to the patient. What (if any) is the placeholder string for made payments, total balance and copays?

Thank you so much!

Dr Schneider.