C++ .dll File Adjustment for UI

I have a .dll file developed in C++ that is currently set up to handle the graphics and animations on my user interface. This file utilizes a __int16, but I need it changed to Long in only one specific place. I'm looking for a proficient C++(Unreal 2.5) programmer who has experience with .dll files and user interface. This is a specific requirement and requires close attention to detail to ensure the file functions as needed after the modification.