Yes, you can definitely add a textbox to your pie chart that shows the total number of points.

1. First, create your pie chart with the two categories - points achieved and points yet to achieve.
2. Next, click on the chart to select it. You should see a "Chart Tools" tab appear at the top of the Excel window.
3. Click on the "Layout" tab within the "Chart Tools" tab.
4. In the "Labels" section of the ribbon, click on the "Data Labels" dropdown menu and select "More Options".
5. In the "Format Data Labels" window that appears, check the box next to "Value".
6. Now, your pie chart should display the values for each category within the chart itself.
7. To add a textbox that shows the total number of points, click on the chart to select it again.
8. Click on the "Insert" tab within the "Chart Tools" tab.
9. In the "Text" section of the ribbon, click on the "Text Box" button.
10. Click and drag your mouse to draw a text box on the chart where you want the total number of points to appear.
11. Type in the text you want to appear in the text box (e.g. "Total points: 140").
12. With the text box still selected, click on the "Home" tab within the Excel ribbon.
13. In the "Font" section of the ribbon, you can change the font, size, and color of the text in the text box to make it stand out.
14. Finally, you can move and resize the text box as needed to make it fit nicely on your chart.

That's it! Your pie chart should now display the values for each category within the chart itself, and you should have a text box that shows the total number of points.