Hello,
Be careful, because CMOD used the numbers of days since 1/1/1970 as a representation of dates. So, if you enter the year as 2099, then ODWEK will automatically refuse the data 2099.
If you enter 99 (as for 2099), then CMOD will think 1999, and then in that case, you won't be able in the query to check that the user did a query with 1999 or 2099.
So I'm not sure in your case, but you can try with the "Permission User Exit", you'll need to parse the sql used to make the query, and change the SQL.
So as Pankaj said, better to change the front end with a fix...
Cheers,
Alessandro