I've seen a similar post to this, but the solution still wasn't quite what I'm needing. I am using Gravity Forms for a camp registration payment front-end.
Some campers receive scholarships of varying amounts. A coupon system wouldn't be efficient, since there are nearly an infinite number of scholarship amounts that could be awarded. What I was hoping for is a "product" field (i.e. scholarship field) that allows a negative number. I've tried that solution, and Gravity Forms accepts the negative amount and adjusts the final total correctly. However, when the user submits to pay, the script returns an error. Is there any way whereby that field's validation routine (i.e. the scholarship field) could allow for negative values? The test page is located: