How to Extend the Trend Line in Excel

1. Open Microsoft Excel 2010.
2. Click the 'File' tab and select 'Open.' Select your file and click the 'Open' button.
3. Right-click the trend line in your spreadsheet file and select 'Format Trendline' from the menu.
4. Locate the 'Forecast' section under the 'Trendline Options.' Type a value in the 'Forward' field to extend the trend line forward, and type a value in the 'Backward' field to extend it backward.
5. Click the 'Close' button.
6. Click the 'Save' icon at the top of the window to save the changes to the file.