I used a named range for the rowsource for the manufacurers combobox. Go to insert-name-define to see how the named range is set up to be dynamic...if you add to or subtract from the column then the range adjusts to the changes.
The rowsource is set in the properties of the combobox14. You will find that it reads "Data" which is the name of the dynamic named range.
The code to add entries through the combobox is:
Private Sub ComboBox14_AfterUpdate()
Dim Rng As Range, c As Range
Set Rng = Range("Data")
Set c = Rng.Find(ComboBox14)
If c Is Nothing Then
Rng(Rng.Cells.Count).Offset(1) = ComboBox14.Value
End If
End Sub
It goes in the code module of the userform2.
One thing you will notice is that the item is not immediatly added to the combobox but is added to the named range on the sheet so the next time you open the userform your new entry will show. That should not be a problem though but just don't expect it to be there until you close and reopen the userform.