how to add checkbox control to Excel Cell dynamically through C# Code on export button click with SQL table Data

In a C# application, I created a button export to Excel. The issue that I am having is that I need to Add Remove column at last as checkbox at the time of exporting excel Report. I have done some searching on google. and found some code, but it's adding CheckBox to entire sheet, not for specific cell.. and also I am not able to see remaining columns and data.. please help find the following code

thanks in advance

dtRequests.AcceptChanges();
string strFilename = "notificationMessage Report_" + DateTime.Now.ToString("dd/MM/yyyy") + ".xls";
Response.ClearContent();
                    Response.Buffer = true;
                    Response.AddHeader("content-disposition", string.Format("attachment; filename={0}", strFilename));
                    Response.ContentType = "application/ms-excel";

                string str = string.Empty;
                foreach (DataColumn dtcol in dtRequests.Columns)
                {
                    string columnName = string.Empty;
                    columnName = dtcol.ColumnName;
                    switch (columnName)
                    {
                        case "GroupName":
                            columnName = "Group Name";
                            break;
                        case "NotificationMessage":
                            columnName = "Notification Message";
                            break;
                        case "PartNumber":
                            columnName = "Part number";
                            break;
                        case "region":
                            columnName = "Region";
                            break;
                        case "Remove":
                            columnName = "Remove";
                            break;
                        default:
                            break;
                    }
                    if (!string.IsNullOrEmpty(columnName))
                    {
                        Response.Write(str + columnName);
                        str = "\t";
                    }
                }
                Response.Write("\n");
                foreach (DataRow dr in dtRequests.Rows)
                {
                    str = "";
                    for (int j = 0; j < dtRequests.Columns.Count; j++)
                    {
                        switch (dtRequests.Columns[j].ColumnName)
                        {
                            case "Remove":
                                str = str+"<html><body><input type='checkbox' value='TRUE'></body></html>";
                                break;
                            default:
                                str = str + Convert.ToString(dr[j]);
                                break;
                        }
                        Response.Write(str);
                        str = "\t";
                    }
                    Response.Write("\n");
                }
                Response.End();