From the SW 2013 Help File:
Global Variables in Configurations
You can configure global variables.
In a design table, the column header for controlling the value of a global variable uses this syntax:
The column header is not case sensitive.
Following these instructions while using $VALUE@OD1@EQUATIONS results in the following error:
"Column Heading ''$VALUE@OD1@EQUATIONS'' contains and invalid feature name ''EQUATIONS''
This is on a very simple part. The variable are defined, so equations should be a valid object as it shows up in the design tree.