subtracting from total: less than zero adds in another space (easy)

Hey guys

I´m an average excel user, using 2003. I´m trying to be more efficient at work.

I´ve got a problem where there are items needed, and items coming in. I want to subtract the items coming in from the items needed, however sometimes there are more coming in than needed. For example:

Coming------Needed-----Missing-----Extra
----10-----------8--------(-2)----------

I want it to be like:

Coming------Needed-----Missing------Extra
---10---------8------------0-----------2

How can I do this? I´m sure I could figure it out with trial and error but I´m using a version in Spanish and I learned in English, and I just want to make sure that what I´m doing is correct so as not to screw up in something very simple and just figure I´m doing the whole thing wrong.

Any ideas? Thanks for your help!

Nick