One workaround
You could hide all the columns and rows outside of the area you want people to see
Unlock all the cells you want them to be able to edit
Protect the sheet
Or, you could leave sheet protection alone, hide columns and rows as mentioned above, and protect the workbook structure
Both of these options would have side effects, but they would do what you are asking without code. A determined user could likely get around them--worksheet and workbook protection do not equal document security
tj