Yes, you can change the tooltip text in an Excel chart. Here's how:

1. Select the chart that you want to modify.
2. Right-click on one of the data points that you want to change the tooltip text for.
3. Click on "Format Data Point" in the context menu that appears.
4. In the "Format Data Point" pane that appears on the right side of the screen, click on the "Tooltip" tab.
5. In the "Tooltip" tab, you can enter your own custom text in the "Tooltip text" field.
6. Click "Close" to close the "Format Data Point" pane.

Now, when you hover your mouse over the data point in the chart, the custom tooltip text that you entered will be displayed. You can repeat these steps for each data point that you want to modify the tooltip text for.