Date Time interval Problem

Hi
I have a problem in which i have to check the time interval to the another which is already exist in Database table.
For Exp.
10:00 am  To 11:00 am i add an Event now if user insert the again this time interval  it's throw the error message.
if user want's to edit this event
For exp.
10:15 am to 11:00 am



how do this.


Thanks



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