dw_1.event itemchanged (row, dwo, data)
if your itemchanged event code uses the dwo object, then you need to supply it.
there is an undocumented function that you can use to get it:
//dwobject __get_attribute( string columnname, boolean )
dwobject ldwo_object
ldwo_object = dw.Object.__get_attribute(ls_columnname, True)