Drupal规则，我该如何拒绝更新节点？

Please help, I can't find a solution. A have rule conditional

function blockcontent_rules_condition_MYCONDITION($node) {
    $n = 2;
    $max = strtotime("+$n day", $node->created);
    if (time()>$max){
         drupal_set_message("somerror");
         return TRUE;
    }
    else {
    return FALSE; } 
}

And it's work, but drupal updating node. How can I deny update node if conditional is true and show error message?

I would create a rule based on the "before saving content" event.