Ask delete confirmation for message delete in mailbox module


i am currently using mailbox module. its good. but i want to modify message delete event. in existing deleting message deleted without ask for confirmation. I want to ask confirmation like "Do you want to delete message?".

Delete button in mailbox.php.

<input type="submit" id="mailbox-action-delete" class="btn mailbox-button" name="button[delete]" value="delete" /> 

Now i don’t know how to use jquery onclick because there is no url defined.

Any suggestion please…