Solidworks & Excel C# Referencing the Design Table

Question

I can't get my design table to modify when opened the line I am having the trouble is var sheet = (Excel._Worksheet)swDoc.GetDesignTable; . Essentially what I want it to do is open the window and reference the active sheet which is the "Design Table". The API does include "DesignTable" as type. I have been stuck for a while. Any help is appreciated.

        //Open Solidworks Design Table
        SldWorks swApp;
        swApp = null;
        swApp = (SldWorks)Activator.CreateInstance(Type.GetTypeFromProgID("SldWorks.Application"));

        ModelDoc2 swDoc = null;
        bool boolstatus = false;
        swDoc = ((ModelDoc2)(swApp.ActiveDoc));
        boolstatus = swDoc.Extension.SelectByID2("Design Table", "DESIGNTABLE", 0, 0, 0, false, 0, null, 0);
        swDoc.InsertFamilyTableEdit();
        var sheet = (Excel._Worksheet)swDoc.GetDesignTable;

        //Generate Linear Guide Support in Solidworks
        if (comboBox1.Text == "0")//No External Rails
        {
           sheet.Cells[6, 4] = "0"; //Cell Location [y-axis, x-axis]
        }