AJAX ConfirmButtonExtender - Confirm Box or Alert Box

Is there a way to change the style of the confirm or alert box when using the AJAX ToolKits

The following works great, there is nothing wrong with it, I just would like to make the confirm or alert box to look different than the normal standard javascript confirm/alert box.

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="atk" %>
<atk:ConfirmButtonExtender ID="ConfirmButtonExtender1" TargetControlID="imgDel" ConfirmText="Are you sure you wish to delete this record?" runat="server" />

I tried using the modernAlert.js but it does not work still display the standard normal alert box.

Thanks