How to change TV modx after saving resource?

Question

MODX

There is a plugin that takes values ​​from the address field and geocodes it into the coordinate field:

<?php
$param = array(
      'adres' => $resource->getTVValue('adres'),
      'id' => $resource->get('id')
      );
$modx->runSnippet('geocoords',$param);

There is such a question:
How to make sure that tv coordinates are not updated if the address is not changed? those. if tv address hasn't changed - don't run snippet