Hi. Not near Max right now, so I haven't tested it, but here's what I would try with a Max mix-map:
What makes it a bit tricky, is that you're using 2 values: the reflection glossiness value is set to 0,65 and the map "strength" is set to 33%.
So first I would put a color map in one mix-slot using a color that equals the 0,65 value. In the other slot I would put the glossiness map, and set the mix to 33%. Then I would set the reflection glossiness value to 1.
As I said, I haven't tested it, but I think it should work.
Hope it helps