validation date range of 2 invalid date inputs

Question

Please help how to trap the validations of if-else-if condition date range of 2 invalid date inputs:

Scenario 1

Download Date From:03/30/2016 
Download Date To:03/31/2016

Process Date From:03/29/2016
Process Date From:03/29/2016

Validation:
Process Date Range From/To is less than the Download Date Range From/To.
error message:Invalid Process Date Range

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Scenario 2

Download Date From:03/30/2016  
Download Date To:03/31/2016

Process Date From:04/15/2016 
Process Date From:04/15/2016

Validation:
Process Date Range are future dates
error message:Invalid Process Date Range.

As i need your big help on this. Thank you Masters