Use the dial() command to insert PIN code

I have a system installed at a company where the CEO is visually impaired. We have an Asterisk box set up as the gateway for Exchange 2007 Unified Messaging and Outlook Voice Access. The problem is dialing the access code (4 digits) and the PIN (6 digits) to get into the UM enabled mail box. I have setup an easy to dial number, 211, and would like it to dial the access code and when Exchange answers dial the PIN code and the # key. So far I have this:

exten => 211,1,Dial(local/6666@from-internal); and this dials into the exchange server, but when I add for the PIN:

exten => 211,1,Dial(local/6666@from-internal||D([203450#])); I get the “cannot complete your number as dialed”

The “D” option is supposed to dial the digits after the call is answered but before the call is bridged.

what am I missing with this? I there a better way to do it?

Thanks
M Wood