private void ApplyChanges()
        {
            double timeWindow = (double)numTimeWindow.Value;

            foreach (TabPage page in tabControl1.TabPages)
            {
                if (page.Tag is GraphItemProperties)
                {
                    GraphItemProperties props = (GraphItemProperties)page.Tag;
                    props.ApplyProperties();
                    props.GraphItem.WindowSize = timeWindow;
                }
            }
        }