How do I replace worksheets in Excel?
 

A project a do at my job is a monthly report using Excel spreadsheets. I enter raw data and get calculated totals, averages, etc. Nothing very complicated. Each worksheet is a month, the workbook is a year. No yearly summary is done.
Now my supervisor wants some new additional info included. Have template for new worksheet.
What would be very nice would be to replace unused pages/worksheets with the new and keep them in one workbook. Can not figure out how to do that.
My alternative is to create a new workbook and label each one appropriately.