[Zope-CMF] How to check if an object exists?

[Josef Albert Meile]

How can I know if an object (ie: a picture) exists?

I have its url, let's say: 
http://localhost:8080/MainPortal/myObjects/test

I know I can make a loop with the "dtml-in" tag, but it isn't the 
best solution, for if you have too much objects on the folder, it 
will take too long.

I have tried to do the following but I got an error because the 
resource doesn't exists:

<dtml-if "REQUEST.resolve_url
('http://localhost:8080/MainPortal/myObjects/test')">
  This resource exist
<dtml-else>
  This resource doesn't exist.
</dtml-if>

I don't have this error when the object exists.
What can I do to know if it exists?