Private Sub GW1_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles GW1.RowDataBound

        If e.Row.RowType = DataControlRowType.DataRow Then
            ' manca il controllo dell'istanza.
            Dim bt As Button = DirectCast(e.Row.FindControl("Btn"), Button)
          
            bt.OnClientClick = "javascript: if (confirm('Vuoi procedere?')) {return true;} else {return false;}"
        End If

    End Sub