Help with formulas calculating card balances and payments

Hi guys,

I need help making a formula that will assist me with my card balances without having to change the formula if the amounts change.

Basically at the moment i have my the full balance of my card, how much is being paid off, how much i have to spend and how much is remaining to be paid off.
Which is fine and a simple full balance minus amount being paid equals amount remaining and the amount to spend is how much i have paid off etc.

However if i go over my available balance, as has annoyingly happened this month, then the formula doesn't work because my available to spend amount wont be what I've paid off because the over balance amount needs to be deducted first. which isn't an issue because i can do a formula for that such as, =SUM(paid off amount-(full balance - credit limit)) which gives me my available to spend amount.

However if my Full balance is less/the same as my Credit limit then the calculation doesn't work.
What i need is a formula so that if the full balance is more than the credit limit then my current formula runs, if not then a simple =SUM(paid off amount + (credit limit - full balance)).

Can anyone help me with this pleaseeeee

I think i may have the attatchment working now.

..and I would consider changing the formatting of your data into simple rows/columns:

Credit card limits are "Opening Balances", Spends are Debits and Payment are Credits: the latter 2 are columns with a third being Current (runniing) Balance.