Excell 2012 for Mac

My issue is that I have formulas in certain cells but would like to lock the formula to prevent it from accidently getting deleted or changed. But I would like to still change the data in those cells without affecting the formulas..

If there is a formula in say, cell C1, there isn't really any "data" there. The "data" is being pulled from other places [i.e. =sum(a4:a6)], or is being calculated by the formula itself within that cell [i.e. =sum(2+2)]. You can't change the "data' without changing the actual formula in that cell. So if you protect the sheet and lock formulas, etc. you won't be able to change the output of the formula unless you change the input.