[Zope] Error trapping Duplicate entry in a database

Hi, I am trying to find a friendlier way of error traping when I am perform some database activities. The one I am looking for first is checking for a duplicate entry in a database. I googled around but I could not find the answer I am looking for. I am using an older version of zope (Zope 2.6.1) and I am still using DTML. Any examples or pointers would be a big help. Thanks in advance, Larry