This may be possible with a computed field using the "sumTimeEntryByGroup()" (hours) or "sumTimeEntrySecsByGroup()" (seconds) functions.
With that said, placing those functions in a field on an item will operate against that item only.
For example, lets say that group "England" adds 40 hours on item 1 and 80 hours on item 2. The new field will have a value of "40" on item 1 and a value of "80" on item 2.
If instead you are looking for a single item holding "120" (which is the total time entered by group "England" across all items in our example), your calcualted field will become more complex as you will need to use aggregate functions such as Query() to return the list of items and then run a Sum of the SumTimeEntryByGroup. Big computations like this can be very slow but are possible.
I would recommend looking through the calculated fields section of the Server Admininstration guide for your version of Integrity to learn more about the functions available.
There are also some knowledgebase articles for running system-wide metrics which may also be useful if you are trying to capture the "120" instead of "40" on item 1 and "80" on item 2.
Hope that helps,