I finally figured out how to do this using Pocket Outlook. It's just a bit of a pain going through all of my meetings and adding this.
To dial a phone number from your calendar, just type tel:â€phone number†without the quotes (e.g. tel:212555457
and hit enter. The phone number should get underlined. If it doesn't get underlined, try some combinations like putting a space after the colon, removing the space, etc. Now when you view the appointment just tap on the phone number and it will dial out.
You can also add an extension to the end if needed, but you may need to add some pauses because some automated systems will miss numbers if they go through too fast.
Example: tel:2125554578,,2,1,4,5,#
Be sure to hit enter at the end of the number or it won't underline.