how to do 2 validations on 1 control end execute and action

I have a TextBox control for the user to manually enter a date.  (customer mandated)
I have an update button on the form that is initally invisible.  Once the user enters a correct date, the update button is visible (from code behind)
To verify the accuracy of the entry, I use:
<asp:CompareValidator id ="inspdatevalidator" runat = "server" Type ="Date" Operator="DataTypeCheck" ControltoValidate = "csc_inspectdateTextBox" ErrorMessage = "Please enter a Valid Date" ForeColor="Red" SetFocusOnError="True"> </asp:CompareValidator>  
I also need to verify that the date entered is <= today (I can do this in code behind if the date is valid)
my problem is I also need to hide the button if for some reason the user goes back and 'messes up' the date.  Because the CompareValidator intecepts the error before the code behind sees it, I can't figure out how ...