In Excel 2007 and Excel 2010, you can use the new COUNTIFS function to count, based on multiple criteria. For example, in a list of orders, you can find out how many orders were for pens, and had a quantity of 10 or more.
I have updated the Contextures COUNT Functions page, to include a COUNTIFS example, and video demo. If you are using Excel 2003, or earlier versions, you can use the SUMPRODUCT function instead. There is an example for that function on the COUNT page too.
Watch the COUNTIFS Video
To see the steps for using the COUNTIFS function, you can watch this short Excel video tutorial.