I keep a set of books for two people, each of whom has several activities. Say for example I have the following qualifiers:

\JONHO for John's house related items
\JONBU for John's business related items
\BILHO for Bill's house related items
\BILBU for Bill's business related items

In your example you would use the qualifier ???BU to get all business-related items. The 3 question marks would mean that any character in that position would be considered a match. So ???BU would return both JONBU and BILBU, but not JOBU. The number of characters is very important.

Note that the qualifier specified looks only at the number of characters you type. So in this example, you select 5 characters --???BU, so the qualifier looks only at the first 5 characters. So you may get unexpected results if you have a lot of different qualifiers that are more than 5 characters long. For example, if you have an account with the qualifier \BOYHOWDY, it would be selected if you use the qualifier \???HO -- even though you're just looking for the "House" items. So the lesson here is to be careful with long qualifiers.