Is there a way to protect only some cells from re-formatting?

Assuming you mean you want to allow them to enter data into the protected cells but do not want them to format the protected cells, do the following (these instructions are for Excel 2019 and the method may be slightly different for earlier versions):

1. Select all required protected cells
2. Go to 'Format > Format Cells'
3. Click on the 'Protection' tab
4. Untick 'locked'
5. Click on 'OK' to exit the dialog box
6. Now go to 'Format > Protect Sheet'
7. Scroll down the list and tick 'Edit objects'
8. Make sure the 'Format cells' option is unticked if it isn't already
9. Optionally browse the list and tick or untick anything else you're interested in
10. Click 'OK' to exit.

That should do it.