Can RegularExpression Control validate mm/dd/yyyy OR empty box as a valid post back?

Can RegularExpression Control validate mm/dd/yyyy or empty text box as true?

 I require the user to enter a date in the valid format or leave empty.

 Currently, if a person enters non-smalldatetime convertable string in the text box, the form fails on post-back.

If I filter the mm/dd/yyyy with a regular expression, the customer can not leave the text box empty.

I am looking RegularExpression Control solution.  I am not looking for a C# or VB solution.

 Thanks for your time,

Sincerely,

 Unhistoric
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