File upload browse button triggers action


I’m new to RoR and I have a file upload form with file_field. Whenever I
use the browse button to select the file name, my action (create) gets
I only want the action to get triggered when the submit button is

Is this possible or should I handle this in my create action,
redisplaying the form if submit was not pressed

How should this be done?

Thanks in advance

Peter van Paassen