Adding MX records to DNS

My client wants to use:
http://www.gfi.com/hosted-email-security/

But can’t add that type of record to the DNS?
They ask me add:
yourcompany.com. IN MX 10 yourcompany.com.pri-mx.smtproutes.com.
yourcompany.com. IN MX 90 yourcompany.com.bak-mx.smtproutes.com.

But the MX record option in the dns page of Direct admin only lets me change the numbers 10 to 90 ?

So how can I add the above 2 records via direct admin dns page ?

Best regards,
joris