asterisk users - Jan 2007 - Add current extension dynamically to template?

Is it possible for a template to know the extension number
in sip.conf?  In the example extension below, I'd like to _not_ have to 
type the lines
username=410
and
callerid=410
in each extension.

Instead, the template should be able to pick up the extension name from 
the [410] extension specified.

In the [grandstream] template example below, I'd like to specify in the 
template that it should use the udername=410.


This is the template:
[grandstream](!)        ; template for Grandstream sip phones
;==============context=default         ;Dials out to telasip-gw for grandstream
type=friend
qualify=yes
insecure=very
host=dynamic
canreinvite=no
nat=no

;add these lines to the template:
username=${extension I am now in}
callerid=${extension I am now in}


This is one of several extension used presently:
[410](grandstream)      ; Karen Office
username=410

I want the extension to have just the line:
[410](grandstream)


Larry

-- 
Larry Alkoff N2LA - Austin TX
Using Thunderbird on Linux