private void btnSpltData_Click(object sender, RibbonControlEventArgs e)
    {
        FieldSelector fs = new FieldSelector();

        fs.ShowDialog();
        if (fs.DialogResult == DialogResult.OK)     // Did user press the 'done' button? or did they exit using X
        {
            foreach (var checkedField in fs.CheckedFields)
            {
                // do stuff with the value
            }
        }
    }