Append same text to every cell in a column in Excel

I just wrote this for another answer:

You would call it using the form using your example: appendTextToRange "[theRange]", ",".

Sub testit()
    appendTextToRange "A1:D4000", "hey there"
End Sub


Sub appendTextToRange(rngAddress As String, append As String)

    Dim arr() As Variant, c As Variant
    arr = Range(rngAddress).Formula

    For x = LBound(arr, 1) To UBound(arr, 1)
        For y = LBound(arr, 2) To UBound(arr, 2)
            Debug.Print arr(x, y)
            If arr(x, y) = "" Then
                arr(x, y) = append
            ElseIf Left(arr(x, y), 1) = "=" Then
                arr(x, y) = arr(x, y) & " & "" " & append & """"
            Else
                arr(x, y) = arr(x, y) & " " & append
            End If
        Next
    Next
    Range(rngAddress).Formula = arr

End Sub