Finding the (Dynamic) End of a Horizontal Range

Hi All,

This one seems so obvious to me and yet I'm having the hardest time using the right combination of HLOOKUP, MATCH, et al.

I'm working on a makeshift Gantt chart for a project management, uh, project and I just can't seem to find the right formula to determine end date. Basically, we've got a series of projects that all have different work rates and start dates, and we have a limited daily capacity to work on those projects. This capacity can be adjusted, however, and depending on how its adjusted, the end dates of these projects can change.

What I need is a formula that will capture what that end date is. Since the date is the top row of my chart, my objective is essentially "find the top row of the last non-zero value in a range given the top row of the first non-zero value in that range". Let me know if you need a visual aid or any additional information and thank you so much in advance!

Ah! The right-most non-zero entry! I spent so much time thinking it had to correspond with the date that I didn't even consider it could be easier than that. Thank you very much!