One idea would be to give the user the option of immediately recalculating, or just displaying the recalculation.  The following are the various states the dynagroups and its members can be in:

dynagroup states - newGroup, toBeDeletedGroup, updatedGroup
child member states - newResourceMember, toBeDeletedResourceMember, noChangeResourceMember

So, if you display the recalculation, it looks the same as a regular calculation, except that the dynagroup rows are highlighted according to their delta.  then, if you click through to some group, each child resource member has appropriate highlighting according to its delta.

maybe there could even be a switch so you can view things like 1) the entire set with delta highlights, 2) the entire delta / just the part that's changing, 3) only the additions, 4) only the deletions, etc.