axlSelectByProperty

Hi all,
I have a script that places external DRC's into a design based off of some checks that are performed. Mostly spacing checks.

I'm trying to generate a list of only the external DRC's by using the command:
   axlSelectByProperty("DRC", "EXTERNAL_VIOLATION_DESCRIPTION")
However it always return:
   nil

If I use the following code I can get my list:

axlSetFindFilter(?enabled (list "noall"  "DRCS") ?onButtons (list "DRCS"))
Drc_List = axlGetSelSet(axlAddSelectAll())

then I can use to determine what type of DRC each on is:

foreach((drc Drc_List drc_t = drc-> type println(drc_t))) --->

"DESIGN"
"DESIGN"
"EXTERNAL REFERENCE"
"EXTERNAL REFERENCE"
"EXTERNAL REFERENCE"
"EXTERNAL REFERENCE"
"EXTERNAL REFERENCE"

....

I have tried various syntax for the axlSelectByProperty() command but always get nil returned.

Am I using the command correctly? If not can somebody help me with the correct syntax?

Thanks in advance,

-K