To use Index Hint with query in axapta you can refer following example where abcIdx is Index name in TestTable. Index hint help to improve performance of query.
TestTable Test_New;
select Count(ProductionId) from Test_New index hint abcIdx group by Test_New.Id
where Test_New.Id == '123' && Test_New.tId == 'was1' &&
Test_New.TransDate >= str2date("01-Jul-2012",123) &&
Test_New.TransDate <= str2date("16-Jul-2012",123) &&
;