Add to Existing Javascript Validation

I need the existing javascript validation modified (see attached) to check and see if the date selected is later than the current date. The date is collected across 3 fields, 'requirednextpaym', 'requirednextpayd', and 'requirednextpayy'. These get the month, day and year across 3 html form elements. The js needs to make sure that the date entered is after the current date. If it is not, it needs to throw an exception that works within the current js validation and notification. The files are attached and all modifications must be clearly commented.