I am trying to do the following:

Sub Sample()
For a = 1 To 100
r = concatenate(Cells(a, 1), Cells(a, 2))
If r = "Mr.Jones" Then
Cells(a, 3) = ""
End If
Next a
End Sub

There is more to it, but I can't seem to use the concatenate function.
"Left", "Right" are ok, but not this one it seems. What am I missing?

Thank you
Chris Cameron