automatic call reference creation

hi all, i need to create an automatic call reference. i though it would work using the date as ccyymmdd and by adding a '001', '002', etc to the end. now, i know how to format the date but how would i increment the 001, 002 at the end... ? i understand that i would have to check back to the database to check the last one used. but how... ? alternatively is to just generate a random number, check it against the database to see if it's not already used. if not use it. if its used already, just create another one... ? OR do you guys have any laternative suggestions ? Regards, Gawie.