Summarising Summary Fields

[lazarus(Legacy Member)]

I have compiled a report which does a comparison between a value (valueA) and a sum of values (valueB).

(ValueA) is displayed in the group section as this is tied to the main identifier of the record, while (valueB) is a sum of some records linked to the main identifier (one to many relationship)

The Group footer of the main identifier has a single record summarising the above, including (valueA) and the sum of (valueB) for the main identifier. Here i have a calculation to find the difference between (valueA) and the sum of (valueB) for each main identifier. The result is (valueC).

Is it at all possible to summarise the result of the calculation above? i.e. Sum (valueC) on the next grouping? Crystal doesn't seem to allow me to, but i'm not sure if someone has tried this or found an alternative method of doing this.

All help/suggestions much appreciated.

(Sorry for the confusing description of this issue. Couldn't think of a better way to describe what i'm trying to do! )