Hello,

That's actually a pretty interesting scenario, because you are saying that the calculations themselves can change, so its not enough to just stop someone from editing the form.    

You are correct in that you could create a new form/content type.    However, I'll throw out another idea:

Utilize two different lists (and two different forms).

The one on the front end will contain your calculations and can be changed whenever needed.   Have a workflow that runs off the first form and essentially copies the values from the first list into the second list.    The second list will be your storage area and will not ever change.   The second list will merely be that of the original items stored in a pristine state that you can view whenever needed.  I would use simple text boxes instead of calculated fields to display the data on the second form / list, this way the values are merely captured at the moment of their creation.     This allows you to modify the front facing form/list calculations whenever desired.

Thanks,

Mike 

That's perfect!  And simpler than I probably would have taken it.   2 forms rather than 4, 5, 6, etc.

I agree it is much simpler to implement as well as protect the original data.   Please mark as correct if you accept this as your solution and glad to have helped.