data validation on subform

[Homegrownandy]

The code I'm working with is below, I only want to check that some data is entered into any field of a subform. Maybe recordset should be used?

It seems to skip past this causing no error where there should be one:

If IsNull(Me.Invoice_Generator2.Form.Controls(Inv_Quantity)) = True Then

Full code listed below. The date validation works ok.

Private Sub Command4_Click()

On Error GoTo HandleError
'''''''''''''
If IsNull(Me.Invoice_Generator2.Form.Controls(Inv_Quantity)) = True Then
MsgBox "Enter at least 1 line value."
Exit Sub
Else
End If

'''''''''''''
If IsNull(Date_on_invoicetxt) = True Then
MsgBox "Please enter a date for the invoice."
Exit Sub
Else
End If

DoCmd.SetWarnings False
DoCmd.RunCommand acCmdSaveRecord
DoCmd.OpenQuery "append invoice lines"
DoCmd.OpenQuery "Update_invoice_issue"
DoCmd.Close acForm, "New Invoice", acSaveYes

DoCmd.SetWarnings True
HandleExit:
    Exit Sub
HandleError:
    MsgBox Err.Description
    Resume HandleExit

End Sub

any help appreciated. its probably simple but I'm very rusty.

[Homegrownandy]

No need to panic guys!

It was as simple as: If IsNull(Me.Invoice_Generator2.Form.Inv_Quantity) = True Then