Order is defined desc or open desc ?
You have REINDEX ?

You can try this:

orderNo = TAGNO('order')
orderExp = KEY(m.orderNo)
orderSingle = PRIMARY(m.orderNo) OR CANDIDATE(m.orderNo)
select 0
use mytable again
scan
  if !SEEK(EVAL(m.orderExp), 'mytable', 'order') OR recno()#recno('mytable') AND m.orderSingle
      ? EVAL(m.orderExp),RECNO(),recno('mytable')
  else
      go top in mytable
  ENDIF
endscan

Not found values have a rule ?
You can post
- expression m.orderExp and its type ?

Fabio