I have a part design where I want to be able to modify the part so that is has a specific value for the mass ...

If I change the material (specifically the density), the distance the base sketch is extruded should update to keep the mass as specified by a CUSTOM property in the file.

Searching the SW support systems claims that the use of CUSTOM properties in equations is possible, but while I can select the CUSTOM property from the drop down menu in the equation editor, the syntax of the inserted text in the equation is deemed invalid.   I have two other CUSTOM properties in my model which I used in defining sketch dimensions, and these transformed into "Global variables" when I entered them into the sketch dimension box.  No problems using them in equations, just the one property which is never used directly.

Has anyone got an example of using a CUSTOM property directly in an equation?