button_to for file_field?

I feel pretty dumb for asking this, but is it possible to just use a button_to for a file upload as part of a form? I want to create a custom "upload file" button. I would just use the good ol' file_field, but apparently you can't customize that with CSS (or rather are limited to what you can customize). I'm currently using CarrierWave to upload multiple files. I would ideally like to use something form_for based. I'm uploading multiple files that have a has_many relationship in a nest开发者_Go百科ed form.

Is there a cleaner approach that I'm overlooking?

You could look at http://swfupload.org/ for fully custom looking file buttons which would allow you to do what you need and also show upload progress etc. The actual standard browser file_field is pretty crappy and in most browsers does not allow much customization.