I am not sure I understand your question.
You can still get a value from a subreport in a 'hidden' section where it is set to 'suppress blank section' becasue it has to run through everything to see if it is 'blank'.
So if you conditionally suppress all of the fields in the section (not the subreport though) and set the section to 'suppress blank section' then you still get the shared variable passed and teh section is not visable.
Is that what you are looking for?