private void abrirToolStripMenuItem_Click(object sender, EventArgs e)
{
if (ventas == null)
{
ventas = new frmventas();
ventas.MdiParent = this;
ventas.FormClosed += new FormClosedEventHandler(close_from);
ventas.Show();
}
}
private void close_from(object sender, FormClosedEventArgs e)
{
ventas = null;
}