Each day I get an Excel file of potential opportunities. The Excel is the input to a workflow that attempts to filter to only those opportunities that meet certain criteria.

The structure of the Excel file remains the same each day. Each Excel input has exactly the same fields. Only the number of entries vary each day. The only other exceptions are the filename and sheet name, both of which reflect the date they were created.
As started, the workflow only accepts one input.
Questions:
- How can I update the workflow such that I can select the file I want to run through workflow?
- How can I update the workflow such that it automatically runs the most recent file added to the source directory through the workflow?
- How can I most efficiently combine all the workflows into a single file and append (join) each new day's file to that master file?
I have attached a crude sample of the workflow as well as 3 sample input days.
Help and thank you.