Hi Ray,
Unfortunately, that's how shared variables work!
You cannot 'read' a shared variable's value coming from the Subreport in the same section or in a section above the section that holds that Subreport.
You'll only be able to access the value in a section below the section that holds the Subreport.
Only workaround is to somehow place the Subreport 'above' Report Footer 'a'.
-Abhilash