Nested Controll Combo Box issues

Hi

I am having a issue with my nested combo boxes on Excel 2003. The ListfillRange of the 2nd combo box is a named range populated using the Offset formula from the value selected in the first combo box. All settings are in the Properties except for a VBA line which resets the default text for the 2nd combo box after an item is selected in the 1st combo box (using ListIndex = 0).

The Issue: The drop down list does not return all values in the named offset range. The number of rows seems to be restricted by the rowcount of the combo box 1 selection from when the spreadsheet is first opened. If I save and open the sheet with the combobox_1 item with the most number of rows (in this scenario the full rowcount appears under combobox_2), and subsequently select an item with less linked rows, the combobox_2 drop down shows blanks and duplicates (not in the source data) - pic is attached. Is there a way to reset the Combobox_2 dropdown settings at the time of selecting an item in Combobox_1?

Thanks is advance.