MySQL: Force to use an Index

Make the mysql query analyzer force use a specific index because i know better:

SELECT fieldA, fieldB, ... 
FROM sometable USE INDEX (IX_DocumentNumber) 
WHERE ...
LIMIT 20;

This is a ‘explain select …’ output:

mysql> explain SELECT ... LIMIT 20\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: sometable
type: range
possible_keys: IX_DocumentNumber
key: IX_DocumentNumber
key_len: 19
ref: NULL
rows: 5122151
Extra: Using where; Using index; Using temporary