By default, Excel locks all cells in a worksheet, but this only becomes
active when the sheet is protected. You will have to unlock all the
cells and then lock only the few that you need, and then protect the
sheet.
To do this, click the intersection of the row and column identifiers -
this will highlight all cells. Then go to Format | Cells and choose the
Protection tab. Unclick the Locked box then OK. Then select the cells
which you want to protect - if these are not in a contiguous block,
then hold the CTRL key down and click on each in turn. Then go to
Format | Cells and Protection tab again and click the Locked box then
OK.
Then go to Tools | Protection | Protect Sheet and a dialogue box will
enable you to choose the protection and decide if you want to apply a
password - if so, you will be asked to retype it (hint, write it down
somewhere so that you can remember what it is).
Now if you try to change anything in the protected cells by
double-clicking on them, Excel will not allow it and will present you
with a warning message.
Hope this helps.
Pete