Hello,
I think the price range you set for this project is a little bit low, however, I am quite new on freelancer.com so I would accept..
It should be easily done though, just to be sure, what do you mean by "combox"?
Of course it's better to use the GUI, elastix has a very good interface I think, and what's more, if you change in the [login to view URL] file directly, any reload on elastix would delete it.. it's in [login to view URL] ;)