Dropdown of users

I'm setting up something like an intranet and I'm hoping to have a gravity form that could be used similar to a contact user form. I'm stuck on how to create a dropdown that is pre-filled in with registered users (specifically, subscriber users.) Is this functionality possible?

Thank you

Better than none, but worse than perfect? I'm familiar with wordpress hooks (I've done plugin development before, but nothing especially credential impressive.)

I've been looking at: http://www.dynamicguru.com/php/how-to-list-all-registered-users-on-your-wordpress-site/ which has

$all_users_id = $wpdb->get_col( $wpdb->prepare(
        "SELECT $wpdb->users.ID FROM $wpdb->users ORDER BY %s ASC"
        , $sort ));

which seems to be in the direction of what I might need?

I've pretty much got it working. For anyone trying to do something similar:

add_filter("gform_pre_render_1", populate_dropdown);

function populate_dropdown($form){

global $wpdb;
$wp_user_search = $wpdb->get_results("SELECT ID, display_name FROM $wpdb->users ORDER BY ID");

//Creating drop down item array.
$items = array();

//Adding initial blank value.
$items[] = array("text" => "", "value" => "");

 //Adding post titles to the items array
foreach ( $wp_user_search as $userid )
	$items[] = array("value" => $userid->display_name, "text" => $userid->display_name);

 //Adding items to field id 8. field_1_2
    foreach($form["fields"] as &$field)

        if($field["id"] == 3){
            $field["type"] = "select";
            $field["choices"] = $items;

        }

    return $form;
}

One thing that's really cool - on the text field I set the default value to be the currently logged in user (me). When I repopulate the field is still sets my user to be the default value (aka it finds me in the list.)

Very cool stuff and excellent support. Thank you.