How do you clear a CustomValidator Error on a Button click event?

I have a composite User control for entering dates:

The CustomValidator will include server sided validation code. I would like the error message to be cleared via client sided script if the user alters teh date value in any way. To do this, I included the following code to hook up the two drop downs and the year text box to the validation control:

<script type="text/javascript">
    ValidatorHookupControlID("<%= ddlMonth.ClientID%>", document.getElementById("<%= CustomValidator1.ClientID%>"));
    ValidatorHookupControlID("<%= ddlDate.ClientID%>", document.getElementById("<%= CustomValidator1.ClientID%>"));
    ValidatorHookupControlID("<%= txtYear.ClientID%>", document.getElementById("<%= CustomValidator1.ClientID%>"));
</script>

However, I would also like the Validation error to be cleared when the user clicks the clear button. When the user clicks the Clear button, the other 3 controls are reset. To avoid a Post back, the Clear button is a regular HTML button with an OnClick event that resets the 3 controls. Unfortunately, the ValidatorHookupControlID method does not seem to work on HTML controls, so I thought to change the HTML Button to an ASP button and to Hookup to that control instead. However, I cannot seem to eliminate the Postback functionality associated by default with the ASP button control. I tried to set the UseSubmitBehavior to False, but it still submits. I tried to return false in my btnClear_OnClick client code, but the code sent to the browser included a DoPostback call after my call.

btnClear.Attributes.Add("onClick", "btnClear_OnClick();")

Instead of adding OnClick code, I tried overwriting it, but the DoPostBack code was still included in the final code that was sent to the browser.

What do I have to do to get the Clear button to clear the CustomValidator error when clicked and avoid a postback?

   btnClear.Attributes.Item("onClick") = "btnClear_OnClick();"

Try adding a return false; at the end of your onClick call. That should prevent the default behavior (in this case submit).

btnClear.Attributes.Add("onClick", "btnClear_OnClick(); return false;")