whi is formula removed but cell value remaining?

Help! I have a series of cells that use index and match functions. I cannot determine how or what triggers this to happen, but the formula gets removed from the cell and only keeps the value. I am not removing the formula, it happens on its own. How do I undo this? Is there a setting that is triggering excel to do this?

Hi,

Have you looked into the event macro ...?
Point to the worksheet tab, right click, view code ...

HTH