Clear cell contents on closing/opening without clearing formulas

I have formulas in 2 cells (C14 and C16) that return results from data input into other cells. When I close the workbook I would like the contents in C14 and C16 to be cleared and wait until new data is input into the other cells before they return a result. This needs to happen without the formulas in C14/C16 being cleared.

Attached file. I'm already clearing input cells but calculation cells need to be cleared after use(upon closing or opening)