How do I specify plane offset value with global variable?

If I try to edit an existing plane or create a new plane using Plane tool in Reference Geometry Tools dropdown box, select a reference plane and attempt to specify the offset with a pre-defined global var "Test" whose value is set to D1@Sketch_Main_Body_Profile, the attempt fails. Can anyone tell me why?
Opening the attached images in numerical order will show you exactly what I'm running into.
Accepted answer

The way to do it is to "link" the plane offset dimension to the "test" global variable.
Right click the plane offset dimension and select "link values", click the dropdown box arrow, and select the "test" global variable.
This should link the plane's offset value to the value which the variable resolves to.
Make sure the variable is defined before trying to link to it, or there will be nothing in the dropdown box.
1 Other answer

After you have got created the offset plane, double click on on that and offset size will display up. Double click on on that measurement and then you could use both <a href="https://usawriters.org">website</a> fee or equation to set that dimension equals to the worldwide variable already defined.