Best way to enable/disable calculations.

Based on the contents on an initial field, I want to enable/disable calculations for a number of other fields.

My solution is to scan the initial field (to see if it's empty) and then in each field I want to enable/disable, just branch into either no code or the calculations I want to perform.

I this a good way to do this?

It seems like it might not be the intended/correct way of doing things and I'm worried it might be a fragile solution or not compatible with all readers as I won't have have much access to this form after it's finished.

If anyone has any advice, that would be pretty helpful, thanks.

Alex.