Creating a wrapper dll for unity

Hi, I am new to Unity and I am trying to integrate novint falcon with the same. I have integrated an ran a suimple program with falcon wrapper.dll. Next, I am trying to do this.

HOW TO MODIFY THE FALCON WRAPPER.DLL? I add a function to one of the source files in the project and want it to be exported to falcon wrapper.dll. But the program does not work. The error that I get in visual studio are:

1. Unable to start program Falcon Wrapper.dll

2. In my post build events: do I need to add an xcopy executable. I tried to add the path- C:\Falcon\$Falcon Wrapper Source\xcopy.exe" in quotes but I get the error Error 2 error MSB3073: The command ""C:\Falcon\$Falcon Wrapper Source\xcopy.exe" :VCEnd" exited with code 4.

Thanks Sunil