messaggio di errore con due celle piene

Private Sub Worksheet_Change(ByVal Target As Range)
Dim R As Range, Cella As Range
Dim Colonna As String
    Application.EnableEvents = False
    If Not Intersect(Target, Range("J14:J60")) Is Nothing Then
        Set R = Range("C14:C60")
        Colonna = " C "
    ElseIf Not Intersect(Target, Range("C14:C60")) Is Nothing Then
        Set R = Range("J14:J60")
        Colonna = " J "
    End If
    If Not R Is Nothing Then
        For Each Cella In R.Cells
            If Cella <> "" Then
                Target = ""
                MsgBox "Non puoi scrivere in questa cella se colonna" & Colonna & "non è vuota."
                Exit For
            End If
        Next Cella
    End If
    Set R = Nothing
    Application.EnableEvents = True
End Sub