Josh - there's a ton of ways you can do this; the "big answer" is more than I can post here. My advice to you is to approach this by breaking it down into smaller and smaller pieces, "thinking like a computer." For example, your first message actually indicates you need to do these things:
- Get a list of all files in a directory
- Open each file and read the contents
- Search the contents for the string "Payment Due" followed by a date
- If the date matches what you're looking for (i.e. it's later than today, or equal to a certain date, etc.) then do whatever you want to do (print the file, reformat the file, etc.)
- If necessary, write the new file back to disk.
- Repeat steps 2-5 for all the files in the directory.
Hope this helps get things moving in the right direction.
best,
Eric