Strangely enough I have been dumb enough not to think of this one and many people havn't either. Here is is for those designers who would find it useful.
<Effect name="Change Units in Area around army">
<Param name="SrcArmy" dispName="$$22300$$Center Unit" varType="group">default</Param>
<Param name="Dist" dispName="$$22303$$Radius" VarType="float">10</Param>
<Param name="FromPlayerID" dispName="$$22453$$From Player" varType="player">0</Param>
<Param name="ToPlayerID" dispName="$$22454$$To Player" varType="player">2</Param>
<Param name="FromType" dispName="$$23771$$FromType" varType="string">Unit</Param>
<Param name="ToProto" dispName="$$23772$$ToUnit" varType="protounit">Axeman</Param>
<Command>trArmySelect("%SrcArmy%");</Command>
<Command>trUnitChangeInArea(%FromPlayerID%,%ToPlayerID%,"%FromType%","%ToProto%",%Dist%);</Command>
</Effect>