Multiple Selection of Sales id in Lookup of Form

public void lookup()
{
    //super();

    Query                           query = new Query(queryStr(ANA_OGSOpenOrders));
    QueryBuildDataSource            qbdsSO;
    container                       cnt;
    SysLookupMultiSelectGrid        SysLookupMultiSelectGrid;
    ;

    if(CustAccount.valueStr())
    {
        query.dataSourceTable(tableNum(SalesTable)).addRange(fieldNum(SalesTable, CustAccount)).value(CustAccount.valueStr());

        if (SalesId != null)
        {
            SysLookupMultiSelectGrid::lookup(query, SalesId, SalesId, cnt);

        }
    }
}