>Is it possible for Excel not to include "hidden" fields in any computation I have in my worksheet?

This isn't real pretty, but this is the only way I could see how to do it.
You could lock the cells as well and use the Cell function and see if the protect value is 1 for locked.

For example, let's say cell A1 is locked (and hidden). You could have a formula that you didn't want effected by hidden cells by making the formula something like: =IF(CELL("protect",A1)=1,A1+B1,B1)