question, is the subreport displayed before or after the details that you want to display?
if before, life isn't too bad.
put the subreport in it's own detail band, say detailA...even better it sounds like put in a group header band and create a shared variable in the subreport and assign it, probably, the sum of the Sales Field, unless it is just one line, then assign it the value of the field.... Like:
shared numbervar saleField := {table.salesField};
"" // hides the assignment.
in detail b or the detail section in the main report, conditionally suppress in Section Expert:
shared numbervar salesField;
salesField <= 0
Done.
If the subreport runs/displays after the detail, you will need to run the subreport twice, which makes a less then optimal solution even worse.
Subreports hit the database once per time run, so running a subreport slows the overall execution of a report, so small reports may not notice a hit, but large reports would.
HTH