I overlooked a usefull property...
<property key="scanStatus" type="attribute" onChange="onStatusChange">
<caption>ScanStatus</caption>
<description></description>
<attributeTypes>
<attributeType name="Enum"/>
</attributeTypes>
</property>
<property key="onStatusChange" type="action">
<caption>On change</caption>
<description/>
</property>
explanation is in the docs