Problem deleting multiple records (one after the other) within a form

I'm having difficulty deleting multiple records (one after the other) using a command button on my form. The first delete works as expected, but when I click the delete button a second time, nothing happens.  Debugging has revealed that my combobox (which filters based on its selection) value is NULL.

I think the problem is with the code that sets the combobox value = the OrderNum that's closest to but less than the ID that was just deleted.  I've tried all sorts of combinations but seem to be missing something.

At any rate, here's the code:

Private Sub cmdDeleteRecord_Click()

Dim cn As New ADODB.Connection
Set cn = CurrentProject.Connection

Dim Response As String

MsgBox Me.Order_Num 'null on the second delete
Response = MsgBox("Are you sure?", vbOKCancel, "Confirm Delete")

Select Case Response
    Case vbOK
               
        DoCmd.DoMenuItem acFormBar, acEditMenu, 8, , acMenuVer70
        DoCmd.DoMenuItem acFormBar, acEditMenu, 6, , acMenuVer70
   
        Dim rstMaxRecords As New ADODB.Recordset
        strSQL = "SELECT Max(Order_Num) as MaxRecord FROM tblOrders WHERE MaxRecord < '" & Me.Order_Num & "' "
               
        rstMaxRecords.Open (strSQL), cn, adOpenForwardOnly, adLockReadOnly
        Me.cboOrderNum.Requery
        Me.cboOrderNum = rstMaxRecords!maxrecord
       
    Case vbCancel
End Select

And here's the code for the combobox that filters by OrderNum:
Private Sub cboOrderNum_AfterUpdate()
   
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.Find "[Order_Num] = " & Str(Nz(Me![cboOrderNum], 0))
If Not rs.EOF Then Me.Bookmark = rs.Bookmark

End Sub

Any suggestions?