I just need some advice on how to do this.

We moved a client from 1 host to another, all is fine except for some
reason the MX isn't connecting with the client in cPanel. After 2
weeks of a lot of engineers being unable to fix it, we have decided to
keep hosting there and have the email run through the old hosting
account.

We changed hosting account because the new host is 5 minutes from the office.

We are happy with th decision to host the site at one place and have
the emails go through the previous hosting company, everyone is happy
with this. It should also solve a few problems for other clietns we
have. Please, please can I politely ask that no-one email suggestions
of how to fix the new hosts cPanel system to allow it to connect to
MX, we really don;t have time to try and test all. What we did within
Plesk worked fine, and that's what we are working towards.

The instructions i have to make this change are below. The problem, as
you can see, is with instruction 8. We need to do this Monday at 4pm
GMT, and the web host engineer at the new hosting company is on
holiday.

1) Last thing in the working day have my client domain.com set his
exchange up again to get the emails instead of using POP
2) In our webhosts, set up the account in Plesk and go in the DNS
section of that domain.
3) delete the record "mail.domain.com".
4) Add a new A record
5) make it "mail.domain.com" and point it to the client's exchange address 
6) delete the 2 MX records pointing to Mail Shield and check to see if
mail.domain.com points to the client's exchange addressLog out of
HostNexus's Plesk account.
7) Log into the cPanel of domain.com/cPanel and change the settings
for the MX panel to verify that the MX records points to
mail.domain.com (which now points to the new IP).
8) Within the cPanel for domain.com/cPanel  go in the mail section of
the domain and click Disable
9) After 4 - 5 hours log into cPanel webmail with the new host to
check there are no emails in there, and if there are to resend them to
themselves (so an email for me@domain.com goes to me@domain.com again)

The problem we have is with 8) I can?t see how to do this in cPanel.
An alternative is to set the domain for remote mail delivery rather
than the default local. But I can?t see how to do that either.

Are these things I can do in cPanel, if not what should I do?