Conditions in User Defined Attributes of Purchasing approval rules

Summary:

While defining the User Defined Attributes for approval rules, attribute or hierarchy can be used, but it has no conditions if the list of values is huge.

Content (required):

We have a requirement to use natural account numbers to drive the PO approval rules. We created User Defined Attributes to run the goods and expense line totals and DOA (approval limits) for goods and expenses are different. We currently run the line totals by line type, destination type. We have a situation now such that expense purchases will be based on item numbers with destination type of 'Inventory' (but non-inventory valued), but should go through the expense DOA. We cannot run the totals anymore by destination/line type. We can run the totals by natural account numbers for goods. But