Union - TOP and Bottom

The select statements:
Select Top(200) ID, ColA - ColB From Table
Order by ColA-ColB Asc
 and
Select Top(200) ID, ColA - ColB From Table
Order by ColA-ColB Desc

yield the correct results for the top and bottom 200 records.

I would like to combine the two queries into a single query. I have tried to use a Union.
Select Top(200) ID, ColA - ColB From Table
Order by ColA-ColB Asc
UNION
Select Top(200) ID, ColA - ColB From Table
Order by ColA-ColB Desc
but the UNION fails because of the Order By clauses.

How should I query the top 200 and bottom 200 records in a table with just one query?

Thanks,
pat