Acl + Delay Pool based on download size

[Kris <christian@xxxxxxxxx>]

Dear,

is it possible ? ex : i want to set a delay pool for limit the bw if 
someone download file bigger than 20Mb. and if lower than 20Mb it`ll be 
no delay pool. i know how to use delay pool but i dont know how to set 
ACL to lock the max size >.<  any clue ?