SELECT tblDoc.SSkl, tblStavke.NSN, Sum(tblStavke.Klc) AS KolUlaza
FROM (tblVrDoc INNER JOIN tblDoc ON tblVrDoc.VrDoc = tblDoc.VrDoc) INNER JOIN tblStavke ON tblDoc.BrD = tblStavke.BrD
WHERE (((tblVrDoc.OpisSK)="ul"))
GROUP BY tblDoc.SSkl, tblStavke.NSN;