How to validate input in maintenance view

Hi Colleagues,

      I have met with one question, I need to implement the feature ,that all of the cycle`s start date and end date should not overlap. So when user copy a line , add a line or modify a line ,this check should happens. How should I do this? I only know I can validate one line using field...module. But how could I validate in a bigger scope, in the whole table ?

Thanks very much.

Regards,

Xu Chris