Custom Firefox Script

I am running Firefox 13, OSX and am looking for a custom script. The script would function in the following way: The script would be toggled on/off. Once toggled on, it would navigate to the Activity Log page. The script would then go through the postings, looking for the posts with similar terms: "posted something via Mob Wars." "posted something via Mob Wars: La Cosa Nostra." The script could be customized to add or remove different games, apps, etc that might post to the Activity Log. Once the script does identify selected posts, it will delete the post appropriately. When complete the script would require no additional input...