Imports Excel = Microsoft.Office.Interop.Excel

Dim ExcelApp As New Excel.Application
Dim ExcelWorkBook As Excel.Workbook
Dim ExcelWorkSheet As Excel.Worksheet

ExcelApp.Workbooks.Open("ExcelFileName")
ExcelWorkBook = ExcelApp.ActiveWorkbook

PreviousSheetName = ExcelWorkBook.Sheets(ExcelWorkBook.Sheets.Count).Name

ExcelWorkBook.Sheets.Add(After:=ExcelWorkBook.Sheets(PreviousSheetName)).Name = "New Sheet Name"