updating hidden fields using gform_after_submission hook - geocoding

Hey guys,

I have been reading this:

http://www.gravityhelp.com/forums/topic/editing-updating-field-value-after-submission

and want to use for the following geocoding on the fly after submission:

// gforms hook for form_#
add_action("gform_after_submission_2", "pre_submission_handler");
function pre_submission_handler($entry){

    // pass the entries relating to the address parts from form
    $query_string = $entry['21'] . "+" . $entry['22'] . "+" . $entry['23'];
    $coords = getLatLong($query_string);

    update_post_meta($entry['post_id'], 'lat', $coords['_wp_geo_latitude']);
    update_post_meta($entry['post_id'], 'lng', $coords['_wp_geo_longitude']);

}

// function to take address and turn it into coordinates lat and lng
function getLatLong($code){

    $mapsApiKey = '(REMOVED FROM POST ONLY)';
    $query = "http://maps.google.com/maps/geo?q=".urlencode($code)."&output=json&key=".$mapsApiKey;

    // This takes your full street address to create the lat/long
    $data = file_get_contents($query);

    // if data returned
    if($data){
        // convert into readable format
        $data = json_decode($data);
        $long = $data->Placemark[0]->Point->coordinates[0];
        $lat = $data->Placemark[0]->Point->coordinates[1];
        return array('Latitude'=>$lat,'Longitude'=>$long);
    } else {
        return false;
    }
}

Except all I need to do is save the geocoded coordinates in 2 hidden gform fields in same form for output later. I believe this example is for saving to post meta instead of the form entry. Any help appreciated thanks.