I've been trying to look online but none of the tuts are really helping me. I am using Microsoft Excel 2010

I'm trying to format my spreadsheet. I have a Gross Rate column and a Net Rate column (about 100 rows).

I want to format the spreadsheet so that if there is nothing at all entered in the cells, the cell will be filled with a color. As soon as any data is typed into that cell, I want the cell's fill to be blank (so white).

I've seen this on other spreadsheets but do not know how to accomplish this.

Thank you very much