In order to get the field ID on a qListForm the customer has to use a developer tool and debug the page (in IE8 and 9 he can use the Developer Tool by pressing F12 and select the Script tab) see attached. Then he needs to search for the label of the field. Once he finds that the very next lane is the field that contains the id of the control.
In the attached image a I have a field FirstName on my qListForm.
Please let me know how it goes.
PS I attached the screenshot but it looks weird. Please let me know if you can see it properly.