asterisk users - Mar 2010 - different authentication requirement

Hi,
I am using the athorisation like this:
_0. => { Authenticate(<file>,a,4); Dial(misdn/g:extern/${EXTEN:1});}

which works fine. So outgoing calls have to be prefixed by "0" and
then asterisk
asks for the code.

But:
The users complain that they have to enter the full number *before* they are 
asked to authenticate. Here is what they want:
Pick up the phone (POST...)
get a tone
dial *8xxx           //xxx is the personal pin number
get a free line including a tone if pin was correct
dial the real number they want to call


How do I achieve this? 

Best regards

Eckhard

> Here is what they want: Pick up the phone
> (POST...) get a tone dial *8xxx           //xxx is the personal pin number
> get a free line including a tone if pin was correct dial the real number
> they want to call
> 
> How do I achieve this? 
Type "core show application DISA" on the CLI.
Authenticate first through extension _*8XXX, then call DISA from there 
with 'no-pasword'.

BTW: misdn is not the most reliable ISDN channel driver.

Philipp