Highlight Cell Once Certain Condition Has Been Satisfied?

I run a small business, and I use Excel to track my books especially receivables.

I have a list of Invoice numbers and Invoice amounts for every customer.

My customers pay periodically (every two weeks, etc), but the tricky part is that the amount paid may not necessarily reflect the exact amount of invoice still being owed. And there may be two, three or five invoices outstanding at any one time.

I have another column which contains payment amount made by customer.

What I would like to do is to highlight the INVOICE NO. cell once the amount of that particular invoice has been bypassed by the total amount paid (i.e. the full amount of that invoice has been paid). Then I can close that invoice.

Here's what my list looks like roughly.

INV NO. - INV AMOUNT - AMOUNT PAID
INV1 ------- 100 ------------- 80
INV2 ------- 250 ------------- 90
INV3 ------- 150 ------------- 80
TOTAL ----- 500 -------------270