Delayed Calculations?

I have a simple script that is subtracting "Field A" from "Field B" to get "Field C"

"Field A" is a user input and "Field B" is read only determined with a simple addition script of other user input fields.

The problem is that as "Field B" changes from the addition of the other user input fields, "Field C" is always one calculation behind.

Is there a way to sequence scripts in fields so that as soon as a value changes, like in "Field A" or "Field B", that "Field C" would automatically change??

Make Sense?

I'm not using varibles right now so I'm not sure if that would help.

Thanks in advance for your time.

-Robert

i can attach code if necessary, but like i said, it's just simple addition and subtraction.