help with Update SQL statement

What am I doing wrong. I am getting the grand total in the update column. I want to sum of Amount_Collected by Id. When I run the Select on it's own I get a total by Id.

UPDATE ##AgencyPerf
SET ##AgencyPerf.PreviousCollected =
(SELECT SUM(dbo.tblCollections_Trans.Amount_Collected)
FROM ##AgencyPerf LEFT OUTER JOIN
dbo.tblCollections_Trans ON ##AgencyPerf.ID_Eclipse = dbo.tblCollections_Trans.ID_Eclipse
WHERE dbo.tblCollections_Trans.Date_Transact < CONVERT(DATETIME, '2002-05-05 00:00:00', 102)
and dbo.tblCollections_Trans.Id_Eclipse = ##AgencyPerf.Id_Eclipse
GROUP BY ##AgencyPerf.ID_Eclipse)
WHERE dbo.tblCollections_Trans.Id_Eclipse = ##AgencyPerf.Id_Eclipse

Thanks,
vmon

It looks like you're trying to update values in a temp table from which you trying to read values from. At least that's what i think you're trying to do. Logically, i'm not sure how this is possible. You might want to use another temp table to hold the values you want to write into the ##AgencyPerf table.