Using negative percentages in Pie Charts

I am having a devil of a time creating a visual pie chart based on the data I am getting from my spreadsheet.

Here is what I am trying to do:

I want to see a visual representation of how many calories I have left to consume before I reach my goal for the day. I have created a spreadsheet that tracks daily caloric intake and gives me a total value. This is a numerical value, like 1600 to 2300. I then have a "goal" caloric value, which remains unchanged. This value is 1800.

The pie chart sees these numbers as positives, so when I put them in you can imagine the result would be close to 50% for both sections of the chart. Obviously, I am inputting garbage values that the pie chart is interpreting accurately.

The next logical step I thought of was to take the "goal" caloric value and subtract the actual "caloric intake" value - this way I come up with a balance of the two - positive or negative. I then used this newly created balance value as "calories remaining" and compared it to "caloric intake."

This seems to give me accurate results, except when I get a negative number in calories remaining. For some odd reason, the pie chart sees this negative number as a positive!?!? For example, if I have a -400 calories remaining compared to 2200 consumed, the pie chart would see this as 400 to 2200.

Any ideas??

Thanks in advance!