See the feature plan for KDE 4.4.
In this section are some ideas and features listened, were discussing about. Maybe these will be implemented in a further release of kdelirc.
VolumeSet(VolumeGet() + 10);
It should be something like:
<action objid="Player" class="volumeup">
<name>Increase volume</name> <comment></comment> <someNewTagName> VolumeSet(VolumeGet() + 10); </someNewTagName>