[Fyren]

If you have the DLL export all its functions, you can use GetProcAddress and the function name to get an address.

Since you have the source, you can also compile it yourself and use the debug symbols Visual Studio generates to find the function and then look at the bytes to make a signature. (I don't know about other Windows compilers.)

You could hook a function called by the function you want, but there's no guarantee some other function won't call the function you hooked. If you can make sure the stack frame above is for the function you really want, sure.