private void cbResUnit_SelectedValueChanged( object sender, EventArgs e )
{
if (edtResolution.Quantity == null)
edtResolution.Quantity = new Quantity();
if (edtResolution.Quantity.Unit == null)
edtResolution.Quantity.Unit = new StandardUnit();
edtResolution.Quantity.Unit.Unit = cbResUnit.SelectedValue as string;
if (_errorLimit != null)
edtErrorLimit.Text = _errorLimit.ToString();
}