Emma,
You don't say which version of Excel you're using. I tried this on
Excel 2002 and it worked fine with no problem. I would double-check
the cell locking on your 10 cells. Note that if any of the 10 cells
are locked, the paste will fail for all 10. Also, if they're trying to
insert, it won't work. Also, when you protect the sheet, make sure
that Select locked cells and Select unlocked cells is checked in the
list, but nothing else. Hope this helps!
James