Drop down list resetting value to 0

Hello,

         I have a WebForm in ASP.Net (VB) that has 2 drop down lists on it.

        The 2nd Drop Down List is populated based on the values from the first drop down list.

        When I select Values from the second Drop Down List, it resets to zero each time. 

        I have tried to capture the event beign fired in the SelectedIndexChanged or TextChanged events but these are not being fired 

        The Drop Down List has AutopostBack = True, EnableViewState=True, CausesValidation=False.

        I do not want CausesValidation=TRUE until the user has entered all of the data on the form, I CausesValidation=True, then all of the fields that do not have entries are flagged

   & ...