One guess hazarded .. perhaps you're asking this ? You can have cells
containing formulas locked against accidental erasure / overwriting.

If say, only col C contains formulas that's to be protected, then try this
sequence. Select the entire sheet, click Format > Cells > Protection tab >
Uncheck "Locked" > OK. Then select only col C, click Format > Cells >
Protection tab > Check "Locked" > OK. Then apply sheet protection via
clicking Tools > Protection > Protect Sheet > Password? > OK. That's it.
Test it out. Only col C would be protected. Elsewhere on the sheet, cells
would be unprotected, allowing for say, data inputs.