Need help with Windows application and DLL codes

Question

I have created a form in DLL which have the list view.
This is how I am displaying the view in the form

private static List<Feature> InitializeLicenseData()
        {
            List<Feature> features = new List<Feature>();
            for (int appID = 1; appID < 6; appID++)
            {
                Random r = new Random(DateTime.Now.Millisecond);
                for (int feature = 1, numfeat = r.Next(4, 7); feature < numfeat; feature++)
                {
                    features.Add(new Feature(
                        string.Format("{0:000}{1:000}{2:000}", appID, r.Next(1000), r.Next(3, 5))));
                }
            }
            m_view = new LMCView(features);
            m_view.Show();
            return features;
        }

This DLL is referenced in a windows application called Test_Client

This windows app have a form which contains a list view, button and a text box.

I need to take the third column of a selected row from this list view and subtract it from the text box value and display this value in the list view in DLL.

Please help me with this.....I am really facing problems to it.