You can create a drop down from a column of cells, but do they really
all need to be in one cell?
If so, you could concatenate (parse?)that list, then populate a named
range with those values, and make the drop down refer to the named range,
whether there are any values in the cells or not.
What is the function to cut your comma separated list into each of its
constituents in a vertical one item per ROW single column fashion?
With that it would be easy. Is it "FIND"? I can do it with a wizard
but I want to make a button that does it from your list. Again, why do
you need to make the desired menu list that way?