Creating a default category on photo upload

When a member posts a photo, I would like to have a DEFAULT category selected.  if I added a hidden field to the form where they upload the photo containing the category, I would want to NOT display the category selections if that variable exists.

I know it's in BxDolFilesUploader.php, just not sure where.

Id' love to just change it to

If (hidden_field){

$category = $hiddenfield;

else

{

normal category stuff here.

}

Come on guys!  Help me out here!  lol!

Somebody has GOT to know this.  There are a bunch of smart people here that know the code.  ;)

 Little confused with this...????

If someone is uploading a picture straight to the wall, they should not have to select what category it goes in, it's being posted to the wall.  so that choice should be made automatically.

Same thing with sound and video.

Just trying to make the wall posting a much smoother experience.