I have run into this issue too many times and need this to be an automated approach:
I have multiple DLL files that are constantly being built/changed that multiple
Use GetModuleHandle to check for the presence of a DLL with the given name. If you want to know if it's a debug version or not, then you need to compile that information into the EXE and check for it somehow. "Debug" vs. "Release" is not a concept built-in to PE format; it's just a set of compile options. Many people put a flag in the version information to indicate whether it's an internal vs. public release.
P/Invoke reference for GetModuleHandle