Generate bob name

Hello

I have a database that we register samples in. We put the samples in boxes with space for 49 pcs. (A01 - G07) per box.
I have made a function to write the same box name, but the users have to put in the name of the box every time the function runs. Is it possible to get access to change the name such as RNA1 first time, run the function, and then on the next run generate the box name RNA2.

Geir Arne