Query Runs Slowly

I have a table with a rotating work order number (from 1 to 9999 then starts over) and because there may be more than one record with the same work order number I need to find the most recent one. Here's the query I'm using the find the most recent record for each work order number:
SELECT * FROM [Work Orders] AS wk1
WHERE NOT EXISTS(
SELECT * FROM [Work Orders] AS wk2
WHERE wk1.[Work Order #] = wk2.[Work Order #] AND
wk1.[Call In Date] < wk2.[Call In Date]
);

Right now the table has a litttle over 10000 records and it takes anywhere from 10 seconds to 60 seconds to return the results. Is there a way I could possibly speed up this query?