Locking Cells and/or Formulas in Spreadsheets

Locking Cells and/or Formulas in Spreadsheets

I am unable to find a way to lock cells and/or formulas.  Also the formulas that I have sometimes delete or change themselves without my input.  I can do a spreadsheet, close and the next time I open it the formulas have moved around on the page referencing different cells then originally intended.