validate a textbox; date

I have a textbox where a date is being entered.   I am using a CompareValidator to check that it's a date. See below.  However, I also want to make sure the date is NOT greater than the current date.     I believe I can also use a CompareValidator to do this; however, when I put two Compare Validators on the page that whose ControlToValidate property is the same text box, this does not seem to be allowed.

Any ideas on how I can do both checks?  


<asp:CompareValidator id="validator_client_dob1" runat="server" display="static" text="*" Type="Date" Operator="DataTypeCheck" ControlToValidate="client_dob" ErrorMessage="Invalid Client DOB.">
</asp:CompareValidator>