How to define the logistics in view table

I create a view table and it contains the date period 'Start time ' and ' End time'.

Now I create the test data like below:

Start time End time Text

2005/01/01 2005/10/12 test 1

2005/02/28 2005/12/31 test 2

The both two date period contains date '2005/08/01',How can I do to avoid to input the repetition period?? In other word , When I input the repetition period ,the system will popup a error message! that is what I want to do...but...I don't really know how to do ....please help me...thanks all.