Running excel 07

I have a table/list created where I log quotes.
Customer / Reference / Quote number
Currently I have a formula in the quote number formula that takes the
previous quote number + 1. So the quote number listed in C10 is 110. As I tab
through it creates a new line and therefore gives me my next quote number ei
111. My problem is, if I were to resort or filter my results, my quote
numbers go out of whack.
Goal: what I want is possibly a macro that as I create a new line, it
converts the value in row C from a formula (=c10+1) to a value of 111.

Any good ideas here?