Defining the coordinates of a point by using global varibles.

Hello, I want to define reference points in 3d Sketch. And I will define some global variables for these points' control vertex parameters. Shortly, I want to make fully defined points in a 3ds sketch. And I want to control this points location according to origin in different configuration. Therefore, I want to use global variables which is defined according to configs. This global varibles will be coordinates of these points. I could not give distance to origin xyz planes because the distance are always positive. However, my variables are sometimes negative. I can not fully control of position of the points. 

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