In order to define a contextual action for cross-plot data nodes, you need to put your Python script in your Python directory under a directory called Contextual_Cross_Plot_Data_Node.
Go to Tools->Options->Environment->Python Scripts (or Tools->Options->Python->Scripts in INTViewer 5.2) and click "Refresh from Disk". Your script should be listed automatically.
You will now be able to execute this script from the contextual menu of the cross-plot data node:
This script will show the key ranges of the cross-plot data in a new dialog window.
This script is attached to the bottom of this article.
The result after the script executes should look something like the following.