Last time I tried this, I gave up on JScript (it seemed impossible) and got something to work in Python.

In JScript, I kept getting errors like “# WARNING : 3392 – Invalid offset specified while extracting data from this attributeÈ.

si = Application
from win32com.client import constants as C            # win32com.client.constants

oObj = si.Selection(0)
oICEAttrMats = oObj.ActivePrimitive.AddICEAttribute("MyString", C.siICENodeDataString, C.siICENodeStructureArray, C.siICENodeContextSingleton)
oICEAttrMats.DataArray2D = [["a", "b", "c", "d"]]

x = oICEAttrMats.DataArray2D
print x
print len(x)
print len(x[0])
print len(x[0][0])

for d in x[0][0]:
    print d


# (((u'a', u'b', u'c', u'd'),),)
# 1
# 1
# 4
# a
# b
# c
# d

See also this Getting DataArray2D attribute values post.