Thanks for the reply. I was also looking at both sites and didn't find this very feature. There's just one thing that caught my eye: At GC, my highest milestone is 1000, 2000 will be my next. At PGC it's the 1500th, with 2000 being presumably the next. Either GC has the 1500th cache but doesn't show it, or PGC has another way to get it.
Getting the nearest milestone and then count to the target is ok for low numbers. Beyond 1000 it gets tedious.