[Zope] Zope - forms being submitted once - inserting duplicate & triplicate data into MS Access database

Hello, I hope that I am submitting this request to the correct channels, please point me in the right direction if I am not. I've come across an issue on the Zope installation which I am managing, where a user will submit one of the many forms, and their result will be posted into the database 2 or 3 times. I've defined a primary key, which does get rid of the multiple entries, but confuses the users with a lengthy error message... Any suggestions as to a better solution to stopping these multiple submissions? I have (in general) an index page calling the dtmlform/method, which on submit calls a second dtml method - which calls the sqlquery, then returning the user to the original form. Thanks and Regards Julian Clark.