Webform; Select List with Dynamic values

Is it possible to fill the select list of a webform with dynamic values, i.e. List of nodes of a specific node type?

1.) I´ve created a node type for scheduling our trainings courses.
2.) I´ve created a webform were our staff could sign up for thiese courses.

Problem:
--> The select list of the possible courses is not dynamic.
--> If a course was cancelled, I have to edit the select list manually.

Any ideas or suggestions?

Sorry for my bad english :))

Piet