As you found out if you suppress the subreport it no longer runs. What you need to do is on your subreport hide all of the fields. On the main report right click on the subreport and click on the last tab. Check the suppress blank subreport checkbox. This will allow your shared variables to still run without showing them. Their will still be a blank space on your main report. If you want to get rid of that go into the section export, and for the band which has the subreport in it, select underlay following section and suppress blank subreport. Now you will not have an empty space either.