I've shared a program called 'saes' which stands for 'sliding AES', you can find the C source code on GitHub released under GPLv2 license.

The idea is to use a scripting language (eg. Python, Perl, Bash) to call this program which will decrypt a file at given offset using a key in another file at a given offset, and finally initialization vector (IV) from a third file at given offset depending on decryption method used."