Need help with multiple IF formulas

I have no idea how to do what my boss is asking. She suggested I come here for help.
We have a retainer payment sheet and we need to keep adding numbers to it as we charge fees or receive payments.

It is set up like this:
Column C is the amount of time for the service
(times) Column D is the rate of the service
(equals)Column E is the total fee for the service
Column F is supposed to reflect the running total if the balance shows a credit
Column G is supposed to reflect the balance if it gets to be negative - so the Doctor knows if she should be collecting more of the retainer.

Following so far?

But she also wants the credit column (F) to change to the current total IF someone makes a payment.
In my example, I have highlighted the row I am having trouble with. A client made a $2100.00 payment. So she wants that column to say $1263.03, like I have manually put in. But how do I get it to do that automatically, if I put $2100.00 in F61?
I feel like this involves an (IF/AND) formula.
Does this make any sense?

Any help is appreciated!

View attachment retainer example.xlsx

I did not understand you well.

try in F61
or try in H61 (if manually you writing in the F column)

A little shorter

=IF(H61<>"",H61+G60,MAX(F60-E61,0))