Change attachment name to text.

Question

I would like to take the name of an attachment and store it in a variable as text.

All the documents uploaded to this library begin with a standard format of 3 char and 2 int(EX: PSF01) I would like to take that PSF01 and store it in a variable to use later when I validate a document type has been added to the folder in question. Any advice for this entire endeavor would be helpful, but I really just need to be able to save an attachment name as text.