display ..... (InventSum _inventSum)
{
    InventDim       joinDim, dimValues;
    InventDimParm   dimParm;
    ReqTrans        reqTrans;

    dimValues.data(_inventSum.joinChild());
    dimParm.initFromInventDim(dimValues);

    select sum(Qty) reqTrans where .......
        #InventDimExistsJoin(reqTrans.CovInventDimId, joinDim, dimValues, dimParm);

    return reqTrans.Qty;
}