Modify the current Budget gauge to use formulas

It would be great if we could use a formula to determine the values for display on the 'Budget' gauge.  We should be able to say If actual costs are within the baseline costs, the gauge should be in the green area, if you are 5% over the baseline costs, it should show in the amber area, and if you are 10% or more than the baseline costs it should show in the red area.  The values and the percentage of baseline cost should be modifiable.