With Desktop alone, you'll need to manually refresh from Excel and pass your colleague and updated twbx file (which they can open in Reader.
If you had Server, you could have the data refresh automatically, and then schedule delivery to your colleague.
There are techniques to automate Desktop tasks (using AutoIt - AutoIt or equivalent), but... how reliable/ stable, I'm not sure.
FYI - You can create a live connection to Excel, so you'll always read the latest data in Tableau, then just to package and send.
I'm sure its not the answer you ideally wanted, but I hope it helps
If you have any questions, please let me know