Diagnosis
You attempted to sum the field mentioned in the warning, but it makesno sense to calculate a sub-total on this control level. This isbecause the control level field comes from a segment which is lower inthe logical database hierarchy than the field you want to use as asummation field.

Procedure
Check that the fields you have selected, the sort sequence and thefields you intend to use for summation really make sense as a completedefinition.