Need some efficient method to Lock/Unlock files

"More StackOverflow geared, but I can't believe something this simple doesn't exist already. Here's the C# code (feel free to modify it, hacked it together quick):

using System;
using System.IO;
using System.Text;
using System.Threading;

class LockFile
{
public static void Main(String[] args)
{
if (args.Length > 2)
{
Console.WriteLine(""Usage: lockfile <file> <wait_in_ms>"");
Environment.Exit(0);
}
string path = args[0];
try
{
File.Open(path, FileMode.Open, FileAccess.Write, FileShare.None);
Thread.Sleep(int.Parse(args[1]));
}
catch (FileNotFoundException e)
{
Console.WriteLine(""File not found, exiting."");
Environment.Exit(0);
}
}
}

Usage:

lockfile c:\somefile.txt 30000

locks the file specified for 30 seconds. When trying to access it you will a message like this:

Here's a compiled binary, .NET framework required. I'll recode it in another language if you need a native binary, just ask in the comments :)"