[Zope] has a folder the 'thumb.jpg' item?

[Catonano]

Hello zopers!

help me please! Please please !

I have some folders like this:

grandfolder
  folder1
    popup.jpg
    thumbpopup.jpg
    thumbpopup_over.jpg    
    genericalFile
  folder2
    popup.jpg
    thumbpopup.jpg
    thumbpopup_over.jpg    
    genericalFile
  folder3
    genericalFile

!! note that the folder3 has NO *popup.jpg files !!
Now:

<dtml-in prefix="folder" expr="grandfolder.objectValues()">
<td> 
<a href="#" 
  onMouseOut="MM_swapImgRestore();
              sfondo(1,'#FFFFFF')" 
  onMouseOver="sfondo(1,'#CCFFCC');
               MM_swapImage('<dtml-var 
pezzo_item>/thumbpopup.jpg','','<dtml-var 
pezzo_item>/thumbpopup_over.jpg',1)" 
  onClick="MM_openBrWindow('<dtml-var 
pezzo_item>/popup.jpg','26NG1103145','width=315,height=265')">
<img border="0" src="<dtml-var pezzo_item>/thumbpopup.jpg" width="60" 
height="50"></a>
          </td>


The problem is that in folder3 it provides a path to some nonexistent 
files!          
I should check wether the folder_item has got the *popup.jpg files and 
draw this cell (<td></td>) ONLY if it has got them, otherwise I 
shouldn't.

How do I check wether a folder contains a given file? i tried 
"folder_item['thumb.jpg']" but when it reaches a folder that doesn't 
contain a 'thumb.jpg' file it breaks! I tried has_key('thumb.jpg'), 
hasKey('thumb.jpg') with no success!

Still, the error it raises when reaching the folder3 folder is KeyError.

Thanks SO much !
Bye
Catonano