Howto derive teh AUTPAR from SARI and IPEI

[tanhh]

System: Aastra/Ericsson TSW SP6

With Aastra Dect system SARI number, we can derive the SARI PARK.

A user brings in a DECT phone which he has accidentally deleted the registration from the phoneset. And unfortunately he never cared what extension number of his dect phone(yeah, we have such users in our organization).

I can get the IPEI by dialling *#06#.

Question:
With the known IPEI, SARI and SARI-PARK number, how can i derive a set of the AUTPAR values?

I wish someone can provide me the calculation method.

Thanks in advance.