Civil 3D VBA selecting featureline in corridor

[Anonymous]

Hi all:
I would like to be able to prompt the user to select interactively a
featureline in a corridor.
Just the way it is done by the "EXPORTFEATURELINE" command in the Corridors
Menu...
I tried the Utility.GetSubEntity method but the object selected is the whole
corridor, not the selected featureline.
Also the returned ContextData variable is empty.
Is there any specific Civil 3D API method that could achieve what I'm
looking for?
Wold certainly appreciate any suggestions.
Thanks in advance,

Reinaldo Togores
University of Cantabria.