Excel 2010 VBA Userform combo box - need to enable user to add new item if not listed in combo box

Hi there,

Thank you for your time in advance.
I have a 2 part question.

1. I have a combo box on a multipage called "cmbx_Last_User_Name" which has a list of people. The user has to make a selection from the list, or if the name is not listed, the user needs to be able to enter it in the combo box.
The new name should then be 'added' to the list, which is a Named Range ("LastUserName") which is contained in the worksheet code named "ws_Validation_List" (not the sheet name).

2. Is it possible to have VBA hard code the named range to be sorted alphabetically from A-Z automatically or would I need 2 option controls, (1) A-Z (2) Z-A and have the user manually sort the list?

I have searched all over the internet and haven't found anything similar, no matter how I word my search, so I don't know where to start from (which procedure would I have to put the code in, the Userform?).

To summarise the names of the controls etc ...

- Combo Box name = cmbx_Last_User_Name
- Worksheet code name where the Named Range is located = **ws_Validation_List**
- Named Range = LastUserName
- Code name of data capture sheet = ws_Incident_Details

I would be immensely grateful for any assistance.

Kind regards,