private void button1_Click(object sender, EventArgs e)
{
neg.CalcularStock(Convert.ToInt32(numericUpDown1.Value), listaStock, listaArticulo, stocks, articulos, tipoArti, tipo);
formu.IsMdiContainer = false;
formu.IsMdiContainer = true;
StockReducido stock = new StockReducido(neg, formu, stocks, articulos, tipo);
stock.MdiParent = formu;
stock.WindowState = FormWindowState.Normal;
stock.Show();
}