Generate list box on active cell selection then place selections from box in active cell

Good Morning,

Looking for code that will show a list selection box when any cell is active in a column. Selections from the list box will be placed in the active cell and the list box will clear and go away when the active cell in said column is not selected. I have a tab with the named list for the box.

Any help is appreciated to get me started.

Data validation will only allow one item selection. I need to be able to select multiple items then have them added to the active cell separated by a comma.