Come integrare 2 funzioni vba

 =Foglio1!$D$31 

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    If Cells(1, 1) = 0 Then End
        If Target.Address = "$C$32" Or Target.Address = "$C$33" Or Target.Address = "$C$34" Or Target.Address = "$C$35" Or Target.Address = "$C$36" Or Target.Address = "$C$37" Or Target.Address = "$C$38" Or Target.Address = "$C$39" Or Target.Address = "$C$40" Or Target.Address = "$C$41" Or Target.Address = "$C$42" Or Target.Address = "$C$43" Then
            If UCase(Me.Range("C31").Value) = "" Then
                MsgBox "Impossibile utilizzare la cella se non hai scritto nella prima."
                Me.Range("D31").Select
            End If
        End If
End Sub