void ventanaCor_Disposed(object sender, EventArgs e)
{
ventanaCor = null;
}
private void menuItem6_Click(object sender, EventArgs e)
{
if (ventanaCor == null)
{
ventanaCor = new frmCortesCaja();
ventanaCor.MdiParent = this;
ventanaCor.Disposed += new EventHandler(ventanaCor_Disposed);
}
ventanaCor.Show();
ventanaCor.Focus();
}