I need a simple way of taking a comma seperated list in a cell, and providing a drop down box to select one of them.

For Example, the cell could contain:
24, 32, 40, 48, 56, 64

And in a further cell, using Data Validation, I want to provide a drop-down list to select ONE of those values

I need to do this without VBA or Macros please.

Apolgies, I want this to work with Excel 2010 and later.
I have been playing around with counting the number of commas in the list and then trying to split this into a number of rows of single numbers etc with no joy yet.