Conditional formating I think?

[FPFWILSON]

I am new to excel and need help writing a formula .If someone could show how to write a formula to accomplish the following I would greatly appreciate it:
I need to add the total in two fields to create the actuall answer as long as it is greater than or equal to 0. If the actual answer is less than 0, the answer should default to 0. i.e.
A1+a2=a3
6+6=12 this would be correct for my puposes.
A1+A2=A3
-6+5=-1 this answer should default to 0, as it is less than 0.
Thank you in advance for your help
FPFWILSON

[NBVC]

Try:

=MAX(A1+A2,0)