Prevent Unlocked Cells Becoming Locked Via Copy/Paste

I have users that are using a protected Excel Workbook where they sometimes have a need to copy values from Internet Explorer paste them into the protected Excel Workbook. When this happens, if the users select the cell and don't actually paste the text into the formula bar (or by double clicking the cell), they can replace the destination cell's formatting - which in this case makes the cells a locked cell instead of a unlocked cell.

Now is there a way to automatically have the pasted value keep the destination formatting? Or perhaps is there a way to set the copy and paste settings so it only pastes text from Internet Explorer into Excel and not the formats?

It is not an option for the userbase to select the option choice of matching the destination formating when pasting as it is a very large user base without much Excel experience.