SELECT Sum([duguje]-[potrazuje]) AS Iznos, Left([stavgk]![konto],3) AS Sink
FROM stavgk
WHERE (((Left([stavgk]![konto],3)) ALike '6%') AND ((stavgk.period)=2014) AND ((stavgk.firmaID)=3) AND ((stavgk.ObracinskiPeriod)="GODISNJI"))
GROUP BY Left([stavgk]![konto],3)
HAVING (((Sum([duguje]-[potrazuje]))<0));