Field Changed event missing valid line number

From the help:

Field Changed*
                                   type: the group (sublist) name
             name: the field name
             linenum: line number if this is a sublist
                                   
                                   Event occurs whenever a field is changed by the user or directly via beforeLoad scripts (nlapiSetFieldValue(fldnam, value, firefieldchanged))

This part:

linenum: line number if this a sublist

This code:

 function OnFieldChanged(type, fieldName, linenum)  {          alert('type: ' + type + ' name: ' + fieldName + ' linenum: ' + linenum);      return;  } 

alerts:

name: item fieldName: item linenum: undefined

Smells broken to me.  Anyone have this working?  Am I missing something??

-Steve