I have a text value in cells A1:D1. Let's say that the values read across
the row:
A1 = "Duck", B1 = "Duck", C1 = "Cat", D1 = "Duck"

I want a formula in cell E1 that will return "No" in this case, meaning that
the items are not all same.

The bit that makes it too hard for me is that there may be blanks, and the
blanks should not be counted. So:
A1 = "Duck", B1 = "", C1 = "Duck", D1="Duck" should be a "Yes" in column E.

Thanks very much for any help.
Daniel