I create a list box through Data|Data Tools|Data Validation. The list box works well but I would like the ability to select multi entries from the drop down list example
You can't do that with Data Validation as it's linked to a single cell. As such, you can only have a single output.
Without knowing more about why you want multiple selections, advice is somewhat limited. You could do 3 different cells where use can make choices, and then concatenate all the answers together...