private void marcaToolStripMenuItem_Click(object sender, EventArgs e)
{
frmDM_Marca o = new frmDM_Marca(null);
o.MdiParent = this;
o.Show();
}
private void btnGoMarca_Click(object sender, EventArgs e)
{
eMARCA o = new eMARCA();
o.MAR_codigo = this.cmbMarca.SelectedValue != null?this.cmbMarca.SelectedValue.ToString() : "";
frmDM_Marca o2 = new frmDM_Marca(o);
o2.MdiParent = this.MdiParent;
o2.Show();
}