Converting simple multiplication formula in VBA code

Friends,

I need a macro coding where i need to multiply the values entered in col G and Col M should get multiplied and reflect the result in column O.

I tried to do this in VBA coding but unfortunately i could not make it...Here is my code.

Can anyone help me to modify it.

Private Sub Worksheet_Change(ByVal Target As Range)
Set isect = Intersect(Target, Range("G:M"))
    If Not isect Is Nothing Then
        If Target <> "" Then
           Range("O" & Target.Row) = Target * Target
            Else
           Range("O" & Target.Row) = ""
          End If
    End If
End Sub