While there's no single foolproof method to completely prevent unauthorized changes to PivotTables in Excel, here are a couple of approaches you can combine for increased protection:

1. Protect the Worksheet:

* This is the first line of defense. By protecting the worksheet containing the PivotTable, you can restrict users from making direct edits to the underlying data that feeds the PivotTable.

Here's how to protect the worksheet:

1. Right-click on the sheet tab containing the PivotTable.
2. Select "Protect Sheet."
3. Enter a password (optional but recommended) and choose the level of access you want to allow.
- Deselect the checkbox for "Select locked cells" to prevent users from even selecting cells within the PivotTable.
- Allow other actions like "Use PivotTable" if you want users to interact with the existing PivotTable but not modify the data.

2. Lock Cells containing PivotTable Formulas:

* Even with a protected worksheet, users might be able to modify the PivotTable itself (depending on your protection settings). To further restrict changes, you can lock the cells containing the PivotTable formulas.

Here's how to lock cells:

1. Select the cells containing the PivotTable formulas (usually located around the PivotTable).
- You can identify these by looking for formulas referencing source data.
2. Right-click on the selected cells.
3. Choose "Format Cells."
4. Go to the "Protection" tab.
5. Check the box next to "Locked" and click "OK."

3. Consider Alternative Sharing Methods:

* If collaboration is needed, explore alternative methods to share the data:
- Use a cloud-based storage platform like OneDrive or Google Drive and grant read-only access for viewers.
- Create a separate sheet with a pre-defined PivotTable for sharing, while keeping the original data and formulas protected on another sheet.

Remember: Password protection can be bypassed by someone with determined efforts. These methods add layers of complexity and deter accidental modifications but cannot guarantee absolute security.