problem with Drop List

I am having a problem with a drop down list that I hope can be solved with minimal effort. I have a workbook with multiple tabs (Jan thru Dec) and all the cells in a certain column have a drop down list. The drop down list is on a separate tab with in the same workbook, but I don’t think that makes any difference. The drop down is a list of our vendors.

I wish to allow the person entering information to be able to type in a vendor that is not within the list on the other tab. I have listed about the top 25 vendors we use. If I were to list all of them, the list would be extremely long and I would still miss some.

How can I allow a vendor that is not on the list to be entered without getting an error message? Can I still make things quicker and easier by providing a drop down list, but still have the option of manually typing in a seldom used vendor. I would normally just add a line, which of course would not have the list arrow then clicked on it and enter the information, but I would lose certain formatting in other columns that I need and the sheet would have to be unprotected also. I allow the necessary cells to accept input by deselecting under “cell – formatting”, but I must protect the worksheet to keep the headers and other cells from getting screwed up by folks who must enter the vendor tickets, but are barely knowledgeable in how Excel works. When the worksheet is protected, you can put info into the deselected cells, but you cannot add a line, so I have reached a dead end there.

I know I could have them click on the cell. Then select “data”, “validation”, and then “any value”, but trust me, these folks would not do it, or do it properly and won’t remember it even if you tattooed it in the back of their hand. Besides, protecting the sheet removes this option also.

Any help would be GREATLY appreciated.