Sub ConcatenateColumns()
'Click the top cell in the right-hand column of data that you want to concatenate. _
For example, if cells A1:A100 and B1:B100 contain data, click cell B1.
Do While ActiveCell <> "" 'Loops until the active cell is blank.
'The "&" must have a space on both sides or it will be
'treated as a variable type of long integer.
ActiveCell.Offset(0, 1).FormulaR1C1 = _
ActiveCell.Offset(0, -1) & " " & ActiveCell.Offset(0, 0)
ActiveCell.Offset(1, 0).Select
Loop
End Sub