private string calcularImporte()
{
string origen = (((this.anterior as Compra.Form4).anterior as Compra.Form3).anterior as Compra.Form1).origen;
string destino = (((this.anterior as Compra.Form4).anterior as Compra.Form3).anterior as Compra.Form1).destino;
SQLManager.ejecutarQuery("select * from [ABSTRACCIONX4].importePasaje('" + origen + "', '" + destino + "')", dgImporte);
return dgImporte.Rows[0].Cells["Importe"].Value.ToString();
}