How to update info on the node creation form right after uploading the image

I hope this is the right place to ask this question.

I am working on a site where users can upload pictures and assign location info to them. The location of the picture is then shown on a googlemap. In case the image holds geo-information, this info is read from the picture using exif module, if not the user has to enter location information manually.

To upload the pictures, i use the imageField widget in CCK. I also use the gmap and location module, and the EXIF Location module to update the location fields.

The gps fields are read correctly from the image and it all works fine, but only after the node has been submitted. What i'd like to achieve though, is that as soon as the image finished uploading, and the widget shows the thumb, the location data in the node/add form is updated and this location is shown on the gmap.

How could i achieve this goal? Is this possible in the standard node/add form, or would i need to make a custom form using the form-api? I am currently working in Drupal 6, but if there is a solution in Drupal 7 i can still change the version.

Any suggestions would be very welcome!

Thanks