If you create a function like this and use it everywhere you want to open an EXE or AppleScript file you can save yourself some trouble. The only "catch" is that you have to use the same base names for your files on each platform.

So if you want to open BOB.JPG you need to create BOBjpg.exe (renamed proxy.exe), BOBjpg.bat and BOBjpg_script and put them all in the fscommand folder. Then you call SmartExec("BOBjpg") and the SmartExec function will figure out which platform you are on and call the correct EXE/script file.

Code:
function SmartExec(target)
{
   platform = $version.slice(0,3);
   if (platform == "WIN") {
      fscommnd("exec", target + ".exe");
   } else {
      fscommand("exec", target + "_script");
   }
}