[Koha] Numeric range searches

I'm wondering if there's a way to do numeric range searches in Koha 3.0 (apart from the ability to search for date ranges in the catalog). The 521 tag, for example, can be used to assign lexiles, reading grade levels, interest age levels, and so on. Ideally, the OPAC should allow a user to identify suitable materials for a child by retrieving items within a range of lexiles, e.g., 420 - 500, and/ or range of reading grade levels, e.g, K-2. Has anyone implemented this? If not, how hard would this be for the development community to implement? Many thanks, Cab Vinton Sanbornton Public Library Sanbornton, NH