Dave,

First, if you examine the accuracy of the forecast, it must stay in the
denominator.
Second, why are you troubled with percentages greater than 100? A 131%
means exactly this: that the actual was 31% more than the forecast.

The second formula I gave you essentially is maybe better for your
thinking. It would return
-25% for a lower actual and +31% for a higher actual. Both are
percentages on the forecast.

Does this help?
Kostis