I have an invoice that on the first page shows a labor subtotal, expense subtotal, then a grand total.

I'd like to now add a field that shows that a retainer/advance has been applied to reduce the subtotals, then give the grand total minus retainer.

If I check the box "apply retainer of $___" the grand total is correct, i.e., it is the total invoices minus retainer already received.

What I'm having trouble with is threefold:

Take a look at this first: look here

First, I cannot find the "button" that shows retainer applied to insert it into a dynamic text area, none of the buttons/paths seem to work, they all give a value of $0.

Second, if possible, I'd like the "retainer applied" field to appear on my invoice only if there is in fact a retainer to be applied, so that I don't need to have two separate invoice templates. I know the standard Billings supplied invoices do that, but I can't find the coding in those invoices to copy over

third, if possible, I'd like to also show the retainer balance, i.e., retainer was $2000, I spent $500, so balance equals $1500, to give the client an update as to what's been spent. Something like "retainer applied / retainer balance" then "$250 / $1500" or something.

Item 1 is a must have, the rest are optional.

Grazie.

Mike