This requires a little amount of network knowledge and the knowledge of any program language to pull it off however you wish:
For this to work you will need a client/server architecture, meaning you will need to create two programs (harsh right?) - one of them is run at the server end - which will do the following:
-When a player logs on it will send a message (like you asked)
-Checks MD5 Hashes against files contained on the server when an MD5 hash is sent…
-It will connect to the client and when client detects a connection, the client will then do it’s thing…
and its thing is this:
-Client will send (most likely) an MD5 hash of most of files in FL known for cheating (such as asteroid fields, speed modding etc.) to the server…
-Server checks them against the MD5 hash of its own files…
If of course the MD5 doesn’t match then something is different and well the player has to be kicked because…well he’s not allowed to be different in FL’s competitive multiplayer environment… lol