OK, I might be the last one to figure this out, but I’m going to post it anyway.

My Garmin only allows 10 proximity points and could never figure out to make proximity points on Map Source. By sheer luck I figured it out!

Right click on the waypoint and click on properties. un-check the unknown box that is right of the proximity box. That will then open the text box where can enter a distance. Type it in the format 0.1 for 1/10 of a mile.

You will have to do this for each cahce, but can come in real handy in places that have heavy cache staturation.