I think I gave the wrong code above.
docs.autodesk.com/CIV3D/2012/ENU/API_Reference_Guide/com/AeccXLandLib__IAeccParcel__GetUserDefinedPropertyValue@[in]_VARIANT@[out,_retval]_VARIANT_.htm
[ id(AECCXLAND_DISPID_PARCEL_GETUSERDEFINEDPROPERTYVALUE), helpcontext(IDH_AECCXLAND_PARCEL_GETUSERDEFINEDPROPERTYVALUE), helpstringcontext(AECCXLAND_HELPSTR_PARCEL_GETUSERDEFINEDPROPERTYVALUE) ]
HRESULT GetUserDefinedPropertyValue(
[in] VARIANT userDefinedProperty,
[out, retval] VARIANT* pVal
);