ExtJS 4.0.7 function handler in button

How do I write a function handler in "button" which is present in the below code so that when we click on that button after providing the "channel url" it will go to that particular "channel url view source" and retrieve "channel name and channel id" from that "channel url view source" and display it in the "channel name and channel id textfield".

[
   {
      formitems:[
         {
            xtype:'dsqfieldcontainer',
            layout:{
               type:'hbox'
            },
            items:[
               {
                  mapping:'ChannelURL',
                  name:'ChannelURL',
                  fieldLabel:'Channel URL',
                  xtype:'dsqtextfield'
               },
               {
                  name:'Look_Up_ChannelID',
                  xtype:'dsqbutton',
                  text:'Button Name'
               }
            ]
         },
         {
            mapping:'CHANNELNAME',
            name:'CHANNELNAME',
            fieldLabel:'Channel Name',
            xtype:'dsqtextfield'
         },
         {
            mapping:'CHANNELID',
            name:'CHANNELID',
            fieldLabel:'Channel ID',
            xtype:'dsqtextfield'
         },
         {
            mapping:'REFRESHTOKEN',
            name:'REFRESHTOKEN',
            fieldLabel:'Refresh Token',
            xtype:'dsqtextfield'
         }
      ]
   }
]

This is the link where my code is available http://ift.tt/1P3ickx