filetype dilemma

[BCE]

I am trying to build an app that will only allow certain file types to be
chosen (for uploading).  On PC, I can just filter out extensions, but on Mac
I need to look at filetypes, and below is the only way I can even get close
to finding out thus far, but if you'll try it, you'll see that some other
info gets stuffed into the button of the answer dialog.  I tried getting the
filetype of the url instead, with the same (more confounded) result.

So basically, even though I can somewhat see what type the file is, it seems
useless with this method.  Any ideas?  Thanks!

on mousedown
answer file "Choose a file:"
answer the filetype of it
--this puts the file path into the answer box's button!
--tried url ("file:" & it) as well with same result, but this inserted
contents of the file into the button!
end mousedown