I don't reckon DTS will do an "Upsert" out of the box.
You'll probably have to use DTS to suck the data into a staging table, and then from there do:
UPDATE U
SET U.Col1 = S.Col1,
...
FROM MyStagingTable S
JOIN MyTable U
ON U.MyPK = S.MyPK
INSERT INTO MyTable
(
Col1, Col2, ...
)
SELECT Col1, Col2, ...
FROM MyStagingTable S
LEFT OUTER JOIN MyTable U
ON U.MyPK = S.MyPK
WHERE U.MyPK IS NULL
If "MyTable" has an IDENTITY column, and you want to preserve the Identity column from the imported data, there is some additional fancy-SQL required.
Kristen