Exchange appointment extended fields via WebDAV

[villian]

I'm accessing Exchange calendar entries using WebDAV, coded in C#.
I need to get the fields on a modified form.
I tried returning all "*" and get only 17 fields back. What should I be searching for to get the fields I'm after?

Form name: AdditionalRequirements

Trying "urn:schemas:AdditionalRequirements"

Thanks!
Victor