Not sure whether you're still onto this thread ...
but think you could also try Debra Dalgleish's sample file at:
http://www.contextures.com/excelfiles.html

Under Data Validation,
look for: DV0017 - Select Multiple Items from Dropdown List

It's a very informative sample
where several techniques are illustrated in different tabs

Since you want the "multi-selected" subjects to be
... all listed in a cell?

the best fit, IMO, is Debra's example in the tab:
CommaSeparated
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Max
Singapore
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