//Helper function: Shows Add Part screen.
public void showAddParts()
{
if (ap == null)
{
ap = new AddParts();
ap.FormClosed += new FormClosedEventHandler(ap_FormClosed);
ap.Show();
}
else
{
ap.Activate();
}
}
void ap_FormClosed(object sender, FormClosedEventArgs e)
{
ap = null;
}