If you start the robocopy process from your application you could check the exit code from there.
Process myProcess = null;
// Start the process.
myProcess = Process.Start("robocopy ....");
myProcess.WaitForExit(1000);
Console.WriteLine("Process exit code: {0}", myProcess.ExitCode);
http://msdn.microsoft.com/en-us/library/system.diagnostics.process.exitcode(v=vs.110).aspx