How can I sort by a field of a subreport?

[gerhard.heil]

Hi all,

I have a report that retrieves 3 attributes attr1, attr2, attr3 from first database, including a subreport that retrieves another attribute attr4 from a second database, and calculates attr5 = attr 2 / attr4. That works so far; the values are displayed correctly.

Now I want to sort the report by attr5. I found the <sortfield> tag, but I need to get the attr5 value from the subreport into the main report. The Return Values property of the subreport seems t do that work, but I get  null as return value. In detail: I have defined a variable $V{returnvalue} in the subreport and a variable $V{returnvalue} in the main report; but I am confused, because in the Add/modify dialog for Return value definition I do not get that variable in the list of Subreport variables, the list contains only the five predefined variables PAGE_NUMBER, COLUMN_NUMBER, REPORT_COUNT, PAGE_COUNT, COLUMN_COUNT (the main report variable is selectable in that list). Should my variable be available in the selection list once I have defined it correctly?

And certainly I need to set the Variable Expression in the subreport, but what is the correct syntay? I tried "$V[returnvalue}=$F[attr5}",  "=$F{attr5}" , "$F{attr5}", without the apostrophes of course; none of them works.

Thanks for any hint.