Filter Drop Down Menu Results

Hi there,

I am reasonably new to excel and I had a question regarding filtering of drop down menus.

In excel 2003, I am using a combination box for a dropdown menu.

I would like data to be entered as follows.
Dropdown box 1 = does it exist Yes or No
Drop down box 2 = if yes then list of stuff if No then only list N/A

As well I find that, the combination boxes don't update when i update the table that it is pulling the list from.
My last question is how can i allow a person to add an item to the menu without showing empty values at the end of the list. I know this is just a check box in the Form data boxes but can't seem to find it for a combination box.

A note is that the end user of this sheet has no knowledge of excel. But does require to update the "list of stuff".

Thanks,

Soupy