title: MaskedEditValidator not working on client side
body: <p>I am trying to enforce 15-minute granularity for time information entered by the user.  So, for example, 12:15 PM and 3:45 am and 9:30 A.M. are all acceptable, but 2:35 PM would not be allowed.  Server-side validation works, but it would be nice if the user was told their input was invalid when the text box loses focus, before they click the submit button.  Here is the code:</p>
  
  <pre><code>        &lt;asp:UpdatePanel ID="UpdatePanel1" runat="server" ChildrenAsTriggers="True" UpdateMode="Always"&gt;
              &lt;ContentTemplate&gt;
                  &lt;asp:TextBox ID="txtStartTime" runat="server" AutoPostBack="True" CausesValidation="True"/&gt;
                  &lt;Ajax:MaskedEditExtender ID="txtStartTime_MaskedEditExtender" runat="server" 
                      TargetControlID="txtStartTime" MaskType="Time" AcceptAMPM="True"
                      Mask="99:99"&gt;
                  &lt;/Ajax:MaskedEditExtender&gt;
                  &lt;asp:RequiredFieldValidator runat="server" ID="StartTimeRequired" 
                      ValidationGroup="EventAddEditControls" ControlToValidate="txtStartTime" 
                      EnableClientScript="True" SetFocusOnError="True"&gt;*&lt;/asp:RequiredFieldValidator&gt;
                  &lt;asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" 
                      ErrorMessage="Invalid time format." ControlToValidate="txtStartTime" 
                      ValidationGroup="EventAddEditControls" SetFocusOnError="True" 
                      EnableClientScript="True" Text="Invalid time format."
                      ValidationExpression="^([1-9]|0[1-9]|1[012]):(00|15|30|45)\s?[aApP]\.?[mM]\.?$" /&gt;
                  &lt;Ajax:MaskedEditValidator ID="MaskedEditValidator1" ControlToValidate="txtStartTime"
                      ControlExtender="txtStartTime_MaskedEditExtender" IsValidEmpty="False" 
                      ValidationGroup="EventAddEditControls" 
                      ValidationExpression="^([1-9]|0[1-9]|1[012]):(00|15|30|45)\s?[aApP]\.?[mM]\.?$" 
                      EnableClientScript="True" SetFocusOnError="True" Text="Time format is invalid."
                      runat="server"&gt;&lt;/Ajax:MaskedEditValidator&gt;
              &lt;/ContentTemplate&gt;
          &lt;/asp:UpdatePanel&gt;
  </code></pre>
  
  <p>How can I get the MaskedEditExtender to enforce the 15-minute granularity constraint on the client side also (assuming that this is possible)?</p>