In SW 2017 you can link a Global Variable to distance between datum plane and inserted one.
In in earlier SW releases I would create a "skeleton sketch", set a Point, link it to coordinate via Global Variable and use Point in a sketch as a reference to the plane you need to insert in a model.
Spasibo I will try and comment if I encountered any problems. Of course I forgot to mention that I have SW 2015, so I will try the second variant.
EDIT: I got it. You can do it via 3D-Sketch with points or planes, but figured out that reference geometry planes also can be linked to Global Variables. You just have to set them first, and AFTERWARDS, you can edit them and insert equations.