You should retrieve the parent like this.
var iRowIndex = oEvent.getSource().getParent().getIndex();
var celID = oEvent.getSource().getParent().getId() +"-col2";
You should retrieve the parent like this.
var iRowIndex = oEvent.getSource().getParent().getIndex();
var celID = oEvent.getSource().getParent().getId() +"-col2";