Select Newest File

We down load a text batch every day from the site to the local computer so we can run it through the carriers program to create the labels for items. I want to speed this up as much as possible thus once the item is downloaded a user should open up a page and it should detect the newest file and then begin to edit this.

(Finds | and splits down by product so I can do type of posting and if 2 items need 1 label then don;t waste or if going royal mail instead put into another database!)

So basically - can I select newest file from folder as there is no easy pattern name wise. In terms of the name the batch number goes up once per day and so it xyz99.txt so I would need to find 99.txt etc...