Highlighting Search Terms

I have a simple script which boiled down to highlighting search terms... Code:

if Trim(Request.QueryString("search"))<>"" then
cont = Replace(cont,Request.QueryString("search"),"<span style=""background-color:#ff0"">"&Request.QueryString("search")&"</span>",1,-1,1)
end if

this worked fine, however if the string I was searching was within an <a> tag, the inevitable would happen and an error would come up. I was wondering if anyone knows a way or if there is a script readily available to tackle this issue?