QueryBuildDataSource.addOrderByField Method [AX 2012]

i am trying to use this method

to sort the results .

for example

 QueryBuildDataSource qbds       = qr.query().addDataSource(tableNum(CustTable));


is good.

  i have a reference column in CustTable   refers to another table   lets say County
  and i County Table recid is in CustTable. 

i need to sort the results on actual value of CountyTable not on  the reference column inside CustTable ie.  County

----- answer could be add County Table as data source .  

without adding County Table to the query.

is that possible? 

your not mentioned Descending or Ascending for sorting

queryBuildDataSource.addSortField(fieldNum(custTable,AccountNum),SortOrder::Descending); //Add sorting

i think its help full