Here is a link to a document I did recently to use a simple workflow to filter an index value. You will use the same principal to extract the parts of the index field containing the file name. You just need to extract the string parts either side of the hyphen.
The workflow is triggered on storage of a document with a specific field empty, in your case, I would trigger it on the filename field containing a hyphen, and the 2 target field being empty.
If your date field, is a true date field then you need to convert the extracted field to a date otherwise the assignment may fail.
Check out the document, and if you need any guidance, just post here.
Senior Director Support Americas