You would have to add the subreport a second time, in a section above the one you want suppressed. So if you want Group Header #1 suppressed and it contains the sub, you would have to insert another GH section, and place a copy of the sub in GH#1a and use a shared variable in the subreport footer that you then pass to the main report to use for suppression purposes.
You can make this GH1a sub "disappear" by suppressing all sections within the subreport, formatting the sub to "suppress blank subreport", removing the borders on the sub, and formatting the GH#1 section to "suppress blank section." As long as you don't suppress the GH#1a section or the subreport object directly, the shared variable will then pass. Then reference the shared variable in the section expert for GH#1b and other sections you want suppressed.
-LB