When you open a workbook, Excel normally displays the worksheet last displayed when the workbook was last saved. You may want a specific worksheet to always be displayed when the workbook is opened, regardless of the worksheet displayed when the workbook was last saved.

You can control which worksheet is displayed by using this macro:

Private Sub Workbook_Open()
    Worksheets("StartSheet").Activate
End Sub

This macro will always display a worksheet named StartSheet. You will obviously need to change the worksheet name to something different; it should exactly match the name of the desired worksheet.

For this macro to work properly, it has to be associated with the workbook object. Follow these steps:

1. Make sure you have only a single Excel workbook open. While this isn't exactly mandatory, it will make creating the macro a bit easier.
2. Press Alt+F11 to display the VBA Editor.
3. In the Project Explorer window you will see a list of the open workbooks and templates. If the Project Explorer is not visible on your screen, choose Project Explorer from the View menu.
4. Locate your current workbook in the Project Explorer. It will be named something like VBAProject (MyWorkbook), where "MyWorkbook" is the name of the actual workbook.
5. If there is a plus sign to the left of the current workbook in the Project Explorer, click on it. You should see a list of worksheets appear underneath the workbook.
6. If you don't see a list of worksheets, but instead see a list of folders with plus signs to their left, click on the plus sign to the left of Microsoft Excel Objects. Now you should see the worksheets.
7. At the bottom of the list of worksheets is the ThisWorkbook object. Double-click on it. A code window is opened.
8. In the code window, paste or create the macro shown above. Make sure you name it exactly as shown.
9. Close the VBA Editor.
10. Save your workbook.

Now, whenever you open the workbook, the specified worksheet will be displayed.