Overview chart about nested tables

Hi,

i created nested tables, like discripted there:
http://www.eclipse.org/birt/phoenix/examples/reports/birt2.1/subreport/index.php

but now i want to create a overview chart about the nested table.

but the chart doesnt contain any data because the dataset doesnt get any data set parameter binding...

how can i solve this problem?

thanks

KR
Flo