It is impossible to write an exporter in GMAX. !!!
All maxcsripting related to exporting or getting any sort of data out
has been removed.
The best you can do is to output to the scriptlistner, but copy/paste is limited to 1500 characters at once, which makes it virtually useless...
If you want to learn scripting the best thing is to analyse what others did and slowly work your way up.
http://www.scriptspot.com/Tutorials.htm
bobo's a good place to start with..