24mg nic base? Or you want the final juice to be 24mg? If you mix 90ml of 36mg nic base into your current nic base, you will have a 24.2 mg nic base. But once you start adding flavoring, it will drop.
EDIT: Are you making your own juice, or is it juice you purchased? From your post, it looks like it is premixed juice we are talking about. If that is the case, do what I just suggested. Buy another 100ml, and mix 90ml into your current 16mg, resulting in 24.2.