How to setup ring group with 1 voicemail

Heres my situation:
I have two extensions, when someone new (who doesn’t know our extensions) calls my business, they hit 1, at the voicemenu, for a (any) representative. In my setup, this forwards the caller to a ring group called “Sales”. If this caller does not get a representative, then they will leave a voicemail. What I need to happen is to have that voicemail to be delivered to two people (two extensions).

My question is: do I need to setup a completely new extension (not that its a lot of trouble) to have this new separate (from any single “user”'s extension) voicemail, thereby removing the “Sales” ring-group altogether? Basically, do I need to setup a new extension with its own voicemail and have that extension setup on line 2 (for example) on our voip phones (in our case, Grandstream gxp-2000’s ), where line 1 is actually our own (for each user) extension, and line two is a “shared” extension over multiple phones (“Sales”)?

Here is how I solved the problem for one site. If someone knows a better way please post it here.

A small number of sales staff responsible for answering incoming calls needed a group mailbox. The small group did not need there own mailbox.

a. All the phones MWI (message waiting indicator) would light when a message was left. b. After one of the sales staff checked the voicemail it would clear all the MWI so there are no duplicate voicemails(customers don’t get call by two ore more sales staff).
c. Message retrieval needed to be simple; by the pressing the message button on the IP phone.

Sales extensions; 601, 602, 603 and 604.

Asterisk is programmed to ring 601, 602, 603 & 604 then go to voicemail after 45 seconds; messages are left in mailbox 600.
All the sales staff check the mail by press in message button on the IP Phone (dials 8500,1,VoicemailMain(${CALLERID(num)}) ).

a. Delete mailbox 601, 602, 603 & 604
b. Create mailbox 600
c.Create a symbolic links in /var/spool/asterisk/voicemail/default/ #ln -s 600 601
#ln -s 600 602
#ln -s 600 603
#ln -s 600 604