target attribut for message body url's

Parsing message body, mhonarc make URLs as <A HREF="...">... </A>, this is
a nice feature, but as I use frame, I need to add a target attribute to
thoses URLs (some one bring action against a webmaster sa print a remote
document in a frame so you can't see the originator of the frame
contents...). 

Regards
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Serge Aumont      CRU  campus Beaulieu             Tel : 02 99 84 71 47
                  35042 Rennes Cedex               fax : 02 99 84 71 67