Are you using the salesperson fields? If not, they could be your sub-territories.
If you are, then I would suggest using the first 3-4 characters (consistantly), as your main territory, then using an additional number of characters for the sub. Then use string functions in report writer and other tools to get the reports you need.
For example: USA0000 as your main territory, and USA0001 thru USA9999 as your sub territories.
In reporting for all main territories, the report could look for USA* or Left([Territory],3) to allow you to combnine all of the subs. You can also parse the field and treat it as if it were two fields as long as you are consistant in the number of digits, or use a common delimiter (like a dash).
