Yes, there is a way to overstrike or combine characters in Excel. Here are the steps:

1. Select the cell where you want to overstrike or combine characters.
2. Click on the "Home" tab in the Excel ribbon.
3. Click on the "Font" group.
4. Click on the small arrow in the bottom right corner of the "Font" group to open the "Font" dialog box.
5. In the "Font" dialog box, check the box next to "Strikethrough" to overstrike the characters.
6. To combine characters, click on the "Effects" tab in the "Font" dialog box.
7. Check the box next to "Overline" to add a line above the characters.
8. Check the box next to "Strikethrough" to add a line through the characters.
9. Click "OK" to apply the changes.

You can also use the keyboard shortcut "Ctrl + 5" to quickly add or remove strikethrough formatting. To add an overline or underline, you can use the keyboard shortcut "Ctrl + Shift + U" or "Ctrl + U", respectively.