view query data in subform

[Gregorys05]

hi i have the below code, and i am trying to set a subform to display the results of a query.
But i keep getting the error "The expression you entered refers to an object that is closed or doesn't exist

any ideas

Private Sub cmdviewinByboxnotindhl_Click()
DoCmd.OpenForm "Form1", acNormal, "", "", , acNormal
SQL = "SELECT TblBybox_Returns_CSV.Meter_Serial_Number" & _
" FROM TblBybox_Returns_CSV LEFT JOIN TblDHL_Returns_CSV ON TblBybox_Returns_CSV.Meter_Serial_Number = TblDHL_Returns_CSV.Mtr_Serial_Number" & _
" WHERE (((TblDHL_Returns_CSV.Mtr_Serial_Number) Is Null));"

Forms![Form1]![Child3].Form.RecordSource = SQL
Forms![Form1]![Child3].Form.Requery

End Sub