Interface Design: Drop Down List Sources

I am working on a workbook that contains drop-downs in various cells. The source for these drop downs are several Named Ranges on a tab named 'Drop Downs'.

I am locking the whole spreadsheet down so that people are not messing with the format, etc. (which is the current problem). So I don't allow people to add/delete rows, etc.

I am trying to think of a good interface to allow users to modify the entries in each drop down list (i.e. they may need to add a person to the "Resources" Range which feeds into a drop-down box elsewhere).

So, people should be able to add/delete items. I was thinking I would put a little 'X' next to each entry, such that when pressed - it would delete the corresponding entry. (Using the Assign Macro on a Text Box). However, I have to assign each 'X' a method to call - and I can't pass in an argument - so if I assign them all the same macro name - I won't be able to figure out which one was pushed. And the number of 'X' will be dynamic, so I can't hard code a bunch of functions. I don't really have a good idea for allowing additions yet (other than a button that prompts for the name and then adds it in).

I guess I could just use a Form that allows editing of the data (that would be easy and powerful to do), but I don't really want to do that - I want it to be editable within the excel spreadsheet itself.