Hiding the lookup elements if the element is assigned with records

public void lookup()
{
  
    Query                                 query;
    QueryBuildDataSource      qbds,qbds1;
    QueryBuildRange              qbr;
    TableA                               tableA                 ;    // the table having form where we insert the lookup           values
    TableB                              tableB ;  // the table from where lookup has taken i.e "Field"
    SysTableLookup sysTableLookup =            sysTableLookup::newParameters(tableNum(tableB ),     this);

    query                         = new Query();
    qbds                          = query.addDataSource(tableNum(tableB ));
    qbds1                         =qbds.addDataSource(tableNum(TableA                 ));
    qbds1.joinMode(JoinMode::NoExistsJoin); // to negotiate the assigned elements
    qbds1.relations(true);
  
    qbr                           = qbds.addRange(fieldNum(tableB ,Field));
    sysTableLookup.parmQuery(query);
    sysTableLookup.addLookupfield(fieldNum(tableB , Field));
    sysTableLookup.performFormLookup();
}