Hi Harlan

At present, it is intended for the workbook this is going into, only one person will be given access to at any given time
I've been able to create a few algorithms/functions that will be used together to create a unique id, so this should greatly reduce any chance of a duplicate

To ensure that only one person can use it at a time, i've created a little macro that checks to see if the workbook is currently open, and if so, it gives the user a little message, and closes the workbook. Plus, i've included as much protection as possible with-in excel

Thanks for you input about the multi-users. It made me think that little bit more about generating non-unique id's

Thanks
PT.