image_attach module and session(drupal 6.x)

I have this form with several form fields and it also accepts image upload by image_attach module. Anyone who has used this module knows that it doesn't use ajax. So, it refreshes the page when uploading and clear up all the filled data inside form fiel开发者_如何学Gods in the process. So, I'm wondering if there is a function in drupal that I could overwrite, and inside this function, I'd like to create session with form fields' data. Is it possible? You help is pretty much appreciated.

Drupal 6.x