My suggestion would be to use an UDF. I think sooner or later, everyone
eventually realizes the need for something like this. This function will
concatenate every cell within a selected range, and you can choose what your
delimiter looks like. Install this into a Module in VBA.
'=========
Function ConcMe(r As Range, Optional x As String = ", ") As String
For Each c In r
'If cell is blank, don't include
If c.Value = "" Then GoTo NoInclude
ConcMe = ConcMe & c.Value & x
NoInclude:
Next c
'Remove final delimiter
ConcMe = Left(ConcMe, Len(ConcMe) - Len(x))
End Function
'==========
Then, back in your workbook, the formula is:
=ConcMe(A1:A50,"_")