I added in a form bij </>Scripts the following code

$max = 300;
// Get a database connection.
$db = JFactory::getDbo();
$db->setQuery("SELECT SUM(`FieldValue`) FROM #__rsform_submission_values WHERE `FormId`='".(int) $formId."'"." AND `FieldName`='Aantal_kaarten'");
$reservations= $db->loadResult();
if ($reservations>= $max) {
$formLayout = 'Sorry, the max reservations arrived..';
}

This ensures that we do not receive more than 300 reservations
Works fine

But now I want to use the value of $reservations
in a Module: mod_rsform_list
I can let show there all the reservations, but is it possible the show there also the summed reservations as in the code above $reservations ?

Or if it is not possible in de mod_rsform_list, just a value on the original entry form