Last day of a given month

[raugust]

Hello, is anyone aware of a way to set a form validation rule such that a DD/MM/YYYY date entry must always be the last day of the month specified?

 

[namliam]

I know how to find the last day of the current month....
Dateserial(year(date()), Month(date())+1,0)

Should be relatively simple to build a before/after update or something to validate it.
Alternatively "simply" force it to the proper date in a query or something.