You could use a caculation field to determine which categerory to put the records into. Something like:
days = C; // Number of days used for aging. Use your exisiting field.
days <= 30; 0;
days <= 60; 1;
days < 90;; 2;
Then sort on this field. Use a leading subsummary section. Put any information you want in the Sub summary section and the records will be listed below.
Great!! Very happy to hear it.