Formula to count only if number is negative

Hello,

I am looking for a formula that will calculate only if the number is negative.

In the attached spreadsheet, I have a Resource pool of 100 and a Contingency of 10. On FWs 28, 30, 31, 32, 33 and 34 (highlighted in Yellow), the number in Teams Available shows as a negative and is displayed in the chart below. I need those numbers to draw from the Contingency instead of showing as a negative.
For instance:
On FW 28, the Team Available is -4 and Contingency remains at 10. The Contingency should absorb the -4 and become 6, returning the Teams Available as a 0.
On FW 30, the -3 in Teams Available should draw from the the Contingency of 10 - returning a Teams Available of 0, and Contingency of 7.

At the same time, the same formula needs to NOT calculate the positive numbers so the Teams Available remains the same and Contingency remains at 10.

Hopefully I explained that well enough! Any help offered would be greatly appreciated! I am not opposed to adding new lines or changing things in order to get the calculations needed.