CLARIFICATION IN XML 2 XML TRANSFORMATION

Greetings all,

I am transforming the XML one to another format. I have an instant in my 
input xml tree like below
<cross-ref refid="bib4 bib5 bib6"><sup>2,4&ndash;6</sup></cross-ref>.

And, after the transformation I need result as below

<sup><a href="#bib2">2</a>, <a href="#bib4">4</a>, <a 
href="#bib5">5</a>, <a href="#bib6">6</a></sup>
Please advise, hot to achieve this.

Many thanks in advance
Arul Kumar