String Builder and ASP.net Controls

I have an application that I need to support.  There is a webcontrol that loops through some data and builds a string of html using StringBuilder and then outputs the HTML to the screen.

I need to make one of the links in the HTML string an asp:HyperLink so I can use to to run some server code.

I have tried adding the asp:HyperLink to the string.  I was hoping that it would still get interpreted as ASP but no go.

Is this possible?  Or is there a better what without totally re-writing the code?