Seeking advice: How can I activate this control without using the built in button?

[spydmobile]

I have a complex form that needs to be filled out (Metadata about the upload) before I can allow the upload of the GPX, I would like my own form elements to trigger the opening of the upload dialog, do I have to hide the button and push it programatically or is there an easier way? Thanks again!

[leplatrem]

Intuitively, I would believe that the easiest way is to hide the button with CSS and trigger a fake click on it :)