1. You could put your label on the report footer of your subreport.
2. Set the Visible property of the label to No.
3. Using the NoData event of the subreport insert the following code.
Private Sub Report_NoData(Cancel As Integer)
Label16.Visible = True
Using your example your syntax maybe incorrect the correct format is
[main report name]![sub report name]![field name on the subreport]