Subtracting a column from a column

[rynorem]

I have two columns, one is number needed and the other is number stocked. How can I get the number stocked column to subrtract from the number needed column. I need to have it done in query. Those are also the title of the columns. Thanks.

 

[Len Boorman]

How about select query to get Number Stocked and Number Needed. Then a derived value

Balance:[Number Stocked ] - [Number Needed]

Len