Hi,

All cells are locked by default when you protect the sheet which you can do with a password.

Use the F5 Goto ket and click the Specials button and tick the 'formulas' option. this will select all the formula cells and you can now format them as Locked with the normal Format Protection menu.

Selct any other cells yuo want to protect and lock them too.

Now switch on sheet protection with a password.