LibraryFeature

HI   I have to change the shape of tubing ( xxx. SLDPRT part ) that are made with a WELDMENT / STRUCTURAL MEMBER with MACRO in vb.NET .   I think I have to use the LibraryFeatureData but I don't knows how to use it.  I found that exermple (http://help.solidworks.com/2010/english/api/sldworksapi/Get_Library_Feature_Data_Example_VBNET.htm) but it don't work. 

In other word, I have to know the the .SLDFLFD used by a STRUCTURAL MEMBER feature, and change it.

Also, what the difference between the GETxxxxx member and the IGET... member.

ThanK for youy help

SolidworksApi macros