Interactice Sorting confusion!

Well I have a data set with the following fields

1) Territory

2) Product Category

3) Sub-Product Category

4) Total Sales

I created a report that is a List with a Nested Table

The List have the Territory Field (and have a grouping on Territory)

And the nested Table Have the other 3 fields Grouped By Product Category

The table group header have the product category fields

And the table details have the sub-category and Total Sales fields

Now to the problem, I have no problem adding interactive sort on the two fields in the table details rows.

But I cannot add an interactive sort to Territory Field in the list or the Product Category in the table group header.

Is this a limitation in interactive sort, they dont sort on fields used for grouping other fields !!!

I also couldn't really understand the interactive field options, the help doesn't really explain them clearly

What does the Options

1- Data Region or Grouping to Sort

2- Evaluate Sort Expression in this scope

How are they really used I dont get it? I tried many options hoping something will work for the territory or product category fields mentioned above, but nothing work!

I hope I was clear

I will try to be more precise I have the following grouping

Territory | Category | Sub Category | Sales

USA

Bike

Bike Mountain 100

Bike Racing 200

Toy

Toy Barbie 50

Toy He-Man 74

UK

Bike

Bike Mountain 100

Bike Racing 200

Toy

Toy Barbie 50

Toy He-Man 74

UAE

Bike

Bike Mountain 100

Bike Racing 200

Toy

Toy Barbie 50

Toy He-Man 74

Terriroty is actually in a text field in the list, where I have a nested table with the other fields group on category in the table group header

I have easily add interactive sort to the subcategory and sales table files, using the default values for the options

I cannot field the correct option combination to add interactive sort for the territory or category fields

Integrity across multiple database types

Since most use SQL server, I thought I would post the question here.
Is it possible, or is there a product or DBMS that enforces referential integrity across multiple databases and database types? Such as SQL Server, Oracle, etc...
Thanks,
ZathDRI(declarative referential integrity) is Peter Chen ERD 1976 enable data delete and update in multiple tables at the same time but you cannot set it up across two databases but if you plan very well you can use linked server to access separate DRI(declarative referential integrity) rules setup in two databases. CASCADE ON DELETE, CASCADE ON UPDATE, ON DELETE NO ACTION and ON UPDATE NO ACTION the later will not allow delete or update. Run a search for all in the BOL(books online). Hope this helps.|||Thanks, just the start I needed.
Zath