Select/Deselect multiple items from data validation drop down

Hello,

I have some VBA that allows me to select multiple items from a data validation list and separate the items with ", " (comma followed by a space). The code also allows you to deselect an item from the list by clicking on the item a second time. The problem arises when you select an item that is embedded within another item. For example, if I have "Daniel" selected from my list and proceed to select "Dan" the result will be "iel". I would like these to be exclusive items where the result would show "Daniel, Dan". I've attached an example file for review.

Thanks so much for any help.

That's what I don't want it to do. I would like each term to be exclusive.

For example, if in cell A1 you currently have selected "Daniel, Aaron, Ron" and proceeded to select "n" you would get the following: "Daiel, AaroRo". I want every term in the drop down list to be mutually exclusive. The result I desire would return: "Daniel, Aaron, Ron, n". Then if you selected "n" again from the drop down the result would return back to "Daniel, Aaron, Ron".

Hope this makes sense.