AutoCAD Civil 3D :: Invoke GetXdata Method On A Label?

I am trying to see what is in the Xdata of a label object:

(setq labl (car (entsel "
Select label: "))
vlabl (vlax-ename->vla-object labl)
)

GetXData is a method of the selected object I am calling vlabl.

I can't figure out exactly how to get this to work. The method list says GetXdata(3). 

When I try 

(setq xdater (vlax-invoke-method vlabl 'getxdata x y z))

I get an error: error: ActiveX Server returned an error: Parameter not optional

If I try

(setq xdater (vlax-invoke-method vlabl 'getxdata 5 5 5))   ;shouldn't this retrieve the values of the array as double double                                                                                     double?

I get nil. No error, just nil. Does this mean there are no values in the array or am I missing a step that lets me read the array?

I was able to convert from variant to safearray for another routine I wrote yesterday, but that variant came from a get-property, not a method. As you can tell, I have hit a wall.