Getting total quantities

Hello List,
I have a situation where I want to figure out the total number of  
products in my database.
I want to read all the fields $ProductStock and add them together to  
get the TOTAL number of products, not just the number of rows in my  
database.
Any pointers on the code to use for adding multiple rows field values?

EG:

Say I have three individual products and Product one has 10 and  
Product 2 has 20 and Product three has 5, and these values are set in  
the field $ProductStock, I want to get the result of 35 and not 3.

Any help is appreciated. TIA

Karl DeSaulniers
Design Drumm
http://designdrumm.com