How is the computer to figure out the user's intent (ie - how will it know
when the purpose for grouping is completed)?

If you have formulae that you don't want overwritten, you can lock these
cells (Format/Cells/Protection) and unlock the cells you want the users to be
able to modify.  Then, apply worksheet protection (Tools/Protection/Protect
Sheet).  The locked cells then should not be overwritten.

Also, if the data is important - it should be backed up.