A1 = 2/15/19 (and date changes daily)
A2 = 2/10/19
A3 = A1 - A2 = 5

Then A1 changes to 2/8/19 and A3 = -2, but I want A3 to "hold" on to 5 unless A1 were to move to something like 2/20/19 then A3 = 10.

I'm trying to keep a hold of the max gap between dates.

First post ever. Thank you for your time.