XML "event" push toward multiple phones (5xi)

Hello

I want to do a thing with xml and I'm searching the good method for this.

Actually I've a softkey on a phone, who change a variable in astdb on the server:
topsoftkey3 type: xml
topsoftkey3 value: http://$$PROXYURL$$/telephonie/xml/stopvoip.php?key=topsoftkey3

This is like the dnd script in "asterisk sample" of Aastra XML Development Toolkit, without "user",

because my script modify a global variable :
topsoftkey4 type: xml
topsoftkey4 value: http://$$PROXYURL$$/telephonie/xml/dnd.php?user=$$SIPUSERNAME$$&key=topsoftkey4

This works very good.

Now I want to update the LED state's of multiple phones when one phone change the variable with his

softkey.
In the xml script, on "change" $action, I can send a xml object to a list of phones for update the

LED state's, but this list will be fixed and will need update each time I modify a key or add a

phone :/
I search the best solution for have a dynamic list: a register at startup/registration and

unregister on disconnection can be an idea ..?

Thanks