Sorry but this can't be done because ... let me explain how the site works.
this is the blog address :

http://amir2download.mihanblog.com/
because its using java to pop-up the comment posting page you have to enter this into the browser url after the site is loaded :

javascript:newComment(10)

and then the page appears !!

now the problem is that the "action" is like this :

action="http://www.gamepack.mihanblog.com/post/comment/new/8/fid/12828237714c76565b983a8/atrty/1282823771/avrvy/0/key/cee8a8c9f46b964922fb12eedc60773c/#post_form