[Please need help] - how to get ID of element hbox

Hi,

I'm newbie and want to edit some script at "image plugin"

       ...                           
       id : 'txtUrl',
       type : 'text',
       label : editor.lang.common.url,
       required: true,
       onChange : function() {
       }
       ...

that piece of script is located in line 485.
and that script is resulted image URL textfield (see image 1 I have attached for the screenshoot).

when I debug this text field using firebugs, this URL text field has id = "177_textInput" sometime the id is changed into other id like "288_textInput", "300_textInput",etc. id name is not consistency .

the question is. how to get the name id of this URL textField?

Attachments:

image 1