How to compare a field value with each title values? I need to compare two field values.

Let's say I have a content type named "Specimen".
The content title is the accepted name of that specimen.
A second field, named Synonyms, can be filled by users to suggest synonyms for the accepted name.

What I need is a field validation with that kind of test :
If the synonym matches any title of that content type, then display a message (That synonym is actually an accepted name already entered in the database) and invalidate the value entered. Else, the synonym is valid and can be entered in the form.

I know Uniqueness which is a great module to compare titles between them but not between a CCK Field and each title (unless I missed something?)

I have tried to configure a test with the module Field validation but did not manage to get a nice result, even with the test "Match against a field". Maybe it was not set properly.

I guess that Rules can be my friend too but for now, I have always created very simple rules. So I would appreciate any help to build this test.
Finally, I found a solution with the module Field Validation and a PHP Code validation rule associated to my field Synonyms:

$args=array(':type'=&gt;'specimen');
$titles=db_query('SELECT title FROM {node} WHERE type = :type',$args)-&gt;fetchCol();
foreach ($titles AS $title){
if ($this-&gt;value==$title){$this-&gt;set_error();}
}


It works like a charm.