GSM call forwarding on specific cases

Hi,

my VoIP extension is on a laptop. If I'm not switched on the extension is unavailable.
The GSM Gateway is connected to my asterisk server.
I have forwarded a SIM card to that very specific extension and I would like to do the following:

1. [align=center]When an incoming GSM call comes in[/align]
   • [align=center]in case my VoIP extension is available (pc running the VoIP client) I would like the phone to ring and if no answer for 6 rings it should be redirected to a mobile phone by the very same GSM card (not through a different GSM card. [/align][align=center](it is possible today with a predefined GSM network call forwarding with AT+CCFC commands, but I cannot set the number of rings before forwarding) it would be better to control the number of rings and the redirection number from asterisk if it is possible[/align]
   • [align=center]in case my VoIP extension is not available I would like to redirect immediately the call to another GSM number (by the SIM card and without routing the call through the GSM gateway to another SIM). In this case I would like to use the SIP response "BUSY". Unfortunately my test [/align]showed me that I cannot use AT+CCFC on busy to do this, because probably the GSM network or the gateway itself is not accepting/mirroring the cause code of the hangup.

[/list][/list][/list][/list]Do you have any description how can I reach the above task?

Thanks.

Case 1:
You must create a routing from GSM to your VoIP extension and predefine the AT+CCFC command.
No other solution but transfered to another SIM out.

Case 2:
Only possible if setup failover routing to another SIM out. Others Negative.