How to create a simple Vacation Request Form Using Infopath 2013?

Hi,

I am trying to create a simple Infopath form that will be used to request Vacations. The only issue is that I can't find a solution to where there is another coworker out in Vacation. The idea is that only 1 coworker can be out at the time. So when selecting what days rage to take as vacation the form should give you a validation error saying "sorry another coworker is out for that date range".

Fields:

1. Member Name (lookup column)
2. Vacation Start Date(date)
3. Vacation End Date(date)

The only thing I am able to do is to show what everybody is having in a repeating table in the form itself.  

I can't find anything in google where the form will not let you take the same day that was already taken. 

Any ideas?

Thanks.