Queries :: Pulling TOP DISTINCT Rows In Final Query

I've got two nested queries. One finds the oldest inspections from an import table, the second compares that query to the main table again and pulls all 'expired' inspections for each Service Order in the first.

These queries are trimmed down for the essential elements of my question. I can post the full SQL if necessary.

queryDoTheseFirst:

Code:
SELECT TOP 18 ImportTemp.[SO ID], ImportTemp.[Inspection Activity],
[Activity Created]+[AddDays] AS [Due Date]
FROM [Priority List] INNER JOIN (ImportTemp INNER JOIN
queryNeededFirst ON (ImportTemp.[SO ID] = queryNeededFirst.[SO ID])
ON [Priority List].Activity = ImportTemp.[Inspection Activity]

[Code] ....

The refinement I would like to make is, rather than having to pull TOP 18 activities in the final query, just pull TOP 12 [SO ID]s and however many activities come along with them (usually 1 or 2, averages out to about 1.5 so 18 is my compromise). In theory an inspector could have two inspections due on every single property, and would only get 9 unique addresses/[SO ID]s. But I can't figure out how to do that when [SO ID] is no longer unique in the second query.

I suppose I could 'number' the rows in the subquery and add a <=12 criteria on that calculated field, but I'm leery of the processing required (that table contains ~14,000 rows, and most methods of numbering seem to want to use DCount).