Add asp:radiobutton to string?

[Cin0s3]

I am using the replace function to try and add a radiobutton into a string but can not figure out how to do it programatically. Any help would be appreciated

strRep=replace("<--add radio1 here-->","<asp:radiobutton runat=server id=radiobutton1/>")
label1.text=strRep

I know that doesn work but not sure how to do it.