@derk:
The short answer is no - I just don't see any way of accomplishing your goal with "out of the box" Flow features. The primary issue is that your Flow will not be able to create calendar entries in a users calendar (unless that user has granted you permissions to do so). Also, you don't have the ability to customize the Flow approval response email.
If there is a solution, it will likely invlove an API call of some type.
If this answers your question, please mark you post as Solved.
Scott
