Writing a DRC rule card to automaticly create a blocking layer

Hi,

Not sure if this is the right place to post this.

I am currently writing a simple calibre DRC card but have come to an abrupt stop.

I would like to identify the perimeter of all the layout cells in a hierarchical GDS called SCX****  , and from this create a GDS layer showing where they are.

Now it is possible to do this in lavis but I thought it would be cleaner if I could do this with calibre.

Regards,

David