Variables in reference geometry

Hello dear members!

I am trying to create a complex reference geometry, from which my parts and sketches will depend. But I can't insert reference planes or axes, that are dependent from global variables (e.g. that would define the distance of two planes from each other). This is necessary to create a laser beam path. How can I make reference geometries dependent on variables?

Thanks,

Maxim

SolidworksDrawings And Detailing