Unlock the cells you want them to be able to change
(Format/Cells/Protection), then protect the sheet.

In article ,
Meenie wrote:

Hi!
I have a worksheet that others need to input data into. I don't want them to
be able to change the size of the cells. They keep dragging the cells into
different sizes causing the thing to print off the page. (They say they don't
know how they did it, lol)
How can I protect the sheet so they can enter their info but not change the
cell sizes?
Thanks, Meenie