[exportforce]

As I wrote, instead of inserting:

<if condition="$attachment['counter'] > 0"> - <a href="#" onclick="whodownloaded($attachment[attachmentid]); return false;">$vbphrase[psiwd_who_downloaded]</a></if>

(Thats what you would normally add)

you take THIS:

<if condition="$attachment['counter'] > 0"><if condition="is_member_of($bbuserinfo, 6, 7, 9)"> - <a href="#" onclick="whodownloaded($attachment[attachmentid]); return false;">$vbphrase[psiwd_who_downloaded]</a></if></if>

And instead of 6, 7, 9 put your usergroup ID's into the code