Hello Adam ,
There is no support for this in the HtmlPLaceholder. A possible solution will be if you are not using a direct HREF attribute in the html link tags, but using a javascript function to navigate instead. This javascript function then can call a Silverlight method from your application and then you can add your custom code.
you can check this msdn article to see how to make the connection between the Javascript and Silverlight:
http://msdn.microsoft.com/en-us/library/cc221414(VS.95).aspx
Greetings,
Valentin.Stoychev
the Telerik team