You can link the file when you embed it. In your Excel workbook, insert an object. Select the Create from File tab and browse to your map. Check the "Link to File" checkbox. Whenever the Excel workbook is opened, the user will be prompted to refresh the link. The problem with this is as long as the Excel workbook is open, your MapPoint file will be locked (toggled as read-only). Another potential problem is that your source file can be edited from Excel (right click, select Map Object and Edit). Doing this will open the file in MapPoint. Whatever changes that are made and saved will be reflected on the embedded object in Excel.