Ext js add to the Ext msg a "don't ask anymore" checkbox

How can I add to my Ext.Msg a checkbox with a text "don't ask anymore" so that the user doesn't have to always confirm that he wants to do a specific action (in my case send a message)?

This is my code:

Ext.Msg.show({
   title: 'Send Message',
   message: 'Are you sure you want to send the message?'
   buttons: Ext.Msg.YESNO,
   fn: function(btn) {
         if (btn === 'yes') {
                 ...
         } else if (btn === 'no') {
                ...
         }
   }
});