private void cmbActsOn_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (Working)
            {
                return;
            }
            FileChanged = true;
            Working     = true;

            CurrentReq.UI_ActsOnCombo_Set(cmbActsOn.SelectedIndex);

            lstRequirements.Items[CurrentReqNum] = CurrentReq.DisplayString();
            lstRules.Invalidate();
            lstRequirements.Invalidate();

            RefreshColorSample();

            Working = false;
        }