I need help with a macro that checks that cells values in column A are
increasing by one increment. In Column A i put receipts numbers. I want to be
able to check if all receipts have been recorded. for example, if column A
looks like this:

A
1 100
2 101
3 103
4 104
5 105

All values are increasing by 1, except the value in cell A3 increased by 2.
Which means that Receipt Number 102 hasn't been recorded.
I want the macro to go through cells in column A, and once it detects a gap,
the cell fill colour (cell A3 in the above example) turns red.

I'm using Excel 2003.

Many thanks
Tendresse