Number Generation

I have multiple users that use a spreadsheet to enter data. I am trying to figure a way to assign a case number to each row of data that is entered. I cannot really do sequential numbers, because often people are entering data at the same time, and often these people are working offline.

So I was thinking if I could somehow have the case number be a few letters (to identify a specific person) and then a series of numbers (to signify which case number it is). That would allow multiple users to enter data offline simultaneously without having to worry that the case numbers are going to be the same. Maybe I could use the Application.UserName and somehow parse it to give me the letters (perhaps Intials or something), and then somehow apply sequential numbers to that...

for instance, JJH00001, JJH00002, etc