[Zope] iterating over different objects in a folder

Hi I've only just started with zope so I hope these are fairly simple questions... I want to be able to display all the documents, images, and files, in a folder in either date or ID order - (not as separate lists for each type). So: Is there an easy way to itterate over the contents of a folder, but returning a single, combined list of files, dtml documents and images? A bit like this... <dtml-in expr="objectValues('DTML Document'[or]'file'[or]'image')"> And if I can get such a list is there a way to test the items to see which type they are so I can display them (or, for files, links to them) appropriately? thanks, John Grey