If c.Value = "" Then

If ActiveSheet.Range("P" & c.Row) = "" Then

Private Sub Worksheet_Change(ByVal Target As Range)
    If Target.Cells.CountLarge > 1 Then Exit Sub
    If Target.Row > 1 And (Target.Column >= 5 And Target.Column <= 9) Then
        Application.EnableEvents = False
            If Target.Offset(, 20).Value = "" Then
                Cells(Target.Row, "P").Value = Date
                Target.Offset(, 20).Value = Target.Value
            Else
                Cells(Target.Row, "Q").Value = Date
            End If
        Application.EnableEvents = True
    End If
End Sub