This won't work for printing, but xl2002 (IIRC), added:
Tools|Formula auditing|evaluate formula
You can step through the formula to see how each portion evaluates.
If you're not running xl2002+, you can select a portion of the formula in the
formula bar and hit F9 to evaluate it. (Hitting Escape will revert the formula
to its original form.)
And ctrl-z will revert the portion you just calculated.
And if you hit enter by mistake Edit|Undo (or ctrl-z) will get it back to where
it was.