Solidworks & Excel C# Referencing the Design Table

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

             //My way around the Csharp Add in 

             SldWorks swApp;

            swApp = null;

            swApp = (SldWorks)Activator.CreateInstance(Type.GetTypeFromProgID("SldWorks.Application"));

            //Macro Generated

            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();

            ModelView myModelView = null;

            myModelView = ((ModelView)(swDoc.ActiveView));

            myModelView.FrameState = ((int)(swWindowState_e.swWindowMaximized));

            var sheet = (Excel._Worksheet)swDoc;

            //Generate Linear Guide Support in Solidworks

            if (comboBox1.Text == "0")//No External Rails

            {

               sheet.Cells[6, 4] = "0"; //Cell Location [y-axis, x-axis]

            }

            else if (comboBox1.Text == "1") //(1) Rail, (1) Runner Block - XY-2 Brkt (R)

            {

                sheet.Cells[6, 4] = "1";

            }

               //Close Design Table

            swDoc.CloseFamilyTable();

SolidworksApi macros