wrote...
I have a relatively large spreadsheet with numerous values
repeated (within the same column) and I would like to merge
adjacent, identical cells.
....

You will almost certainly regret merging cells in Excel. Merged cells
cause many problems, and a number of menu commands, such as sorting,
won't work on ranges that contained merged cells. Also, if B5, C5 and
D5 originally contained "foobar", and you merged B5:D5, you'd DELETE
the contents of C5 and D5. Only B5 would contain "foobar". If you had
formulas that referred to C5 or D5, they might no longer return
correct results.

What do you really want to accomplish? It's a near certainty merging
cells won't do it unless you're only concerned with the appearance of
your spreadsheet.