Custom Formatting on Multiple Cells

I am not very good at explaining problems so I will try my best!:

I am creating a spreadsheet for a stockroom, each product that my business sells, is on an individual row, and the details for each product can be seen in the columns (e.g. Product ID, Product Name, Cost Price, Number Sold, Number Brought, Units in Stock).

What I want to happen, is for rows to be blacked out (through formatting) if the remaining stock levels fall below around 3, then the row that the product is on, is 'un-blacked out' and so can be seen. However if the number of remaining stock is above 3, the row is blacked out.

So the sheet will work that only products with the number of remaining units in stock are below 3, are visable, and the others are blacked out.

Thanks in advance for any help.

See http://www.contextures.com/xlCondFormat01.html

You're welcome.