If you set a hunt group with exta in it then another hunt group with extb call this one ovf. then in the 1st hunt group with exta in the overflow put in the ovf group. set the overflow timer as you wish for both the group. this is what should happen, the call goes to the 1st group if it ring but dose not get answered then it will goto the ovf group if still not answered the it should go back to the 1st groups mail box. In the exta source numbers eneter Hthegroupname this is so you get the light on the phone to say there is a message in the group. The no answer timer must be set greater the the overflowtimer other wise it will trip to voice mail to soon. Make sure the both hunt groups are set to ring groups.
You will not have to set anything for the groups in voicemail pro.

option 1 set ext b to foward no answer to a short cod that goes to mialbox ext b:-

short code xxx - >any digets
tel no "#,<userb>"
feature VoicemailColletct
Option 2 - forward no answer to a squential group
ext1 - extnb
ext2 - dummy ext with fowrard hunt group calls set & forward all set to short code as above
(enables ext b to have personal vm for ddi
option 3 - vmpro (user\group)\leave entry point
 leaveamil - specific\mailbox<(user\groupname)>

if uoy need further examples e-mail ipguru@ntlworld.com & i will try to seng example CFg's

any spamm sen to the above & the arddr will be deleted.
I am willing to help IPO programers but will not be taken advantage off!

PS OPtions 1 & 2 will also work with VM lite!

Whats wrong with setting Ext A to forward on no answer to Ext B.  
On my IP403 1.3, if Ext B doesnt answer, the caller is sent to Ext A's voicemail.

opps drunk too much tonight, thought yu wanted to go to a different VM.
By default VM will always go to first number rung
( I feel a right burk now)

Too easy.

I did not know that you could have a no answer forward and voicemail cover it.

Thanks that worked!

On the assisted transfer problem:

I have had problems with the ass. transfer too. Together with our supporter, we found out that ass. transfer only worked, if there was a wav-file in the playlist...

Workaround: Creating a 0,01s empty wav for playback.

This is a current problem in Denmark/Sweden

If you put a fwd on the exta the if anyone calls that ext internal the there call will also goto extb not good if they have a call for exta but want to leave a voicemail for that ext