[Zope] how can i the height of a image

hi, in a file index_html, I search to have the height of a image, but this, is in a subdirectroy called "images" After a request of a database, I have the name of the image in a variable "nom" if I write < dtml-var expr='images.'+nom+'.height' > the result is images.x0y0.height (x0y0 is the name of my image,) if I write < dtml-var expr='images.x0y0.height' > the result is 275 ok, it's the height of my image how to make to have the first sentence, but with the result is "275" ? thank - - -- by AlainBB http://www.barbason.be