yes indeed, read up on sessions. the basic idea would be to start a new session when some runs your script which would log the date/time. the next time that the script is run you simly check to see if the log time is set and if it is 2 minutes old. this however is not entirely fool proof as there are easy ways for users to kill their session and re-run your script. you could also do an IP check but this too is not entirely reliable.