Help with MX on DNS someone pls.

Hello everyone.
 
If someone can pls help. We have an HC6 which we unfortunately cant currently upgrade to HC8. Its integrated with SimpleDNS on the same box. There's no secondary HC, since simpleDNS itself does the sync to the secondary SimpleDNS on other box.
 
I wanted to know where, in HC6, I can setup for it to create a secondary MX... In HC Settings and logged as HCADMIN in name server settings I see only the option to create 2 CNAMES... And secondary MX priority. But I dont see where I can set which host the secondary MX points to :(

See images:
http://screencast.com/t/luPS52ikn
http://screencast.com/t/zd7JXqNGxt
Any ideas?

Thanks!