Conditional formatting and subtraction

Hello all,

I'm creating a budget sheet and I've used conditional formatting to fill in a couple of cells which change colour when the word "Paid" is entered. There's a column which contains a running total of money owed and I want to subtract the "Paid" items from this total. I can't think of a formula that will do this. Is it possible? I attach an example of the spreadsheet. I would like to subtract the items in columns E and G from the totals at the bottom once the items have been marked "Paid".

I hope someone out there can help me.

Kind regards
Bizzielizzie