[Serusers] Setting tm module parameter "fr_inv_timer_avp" more than once during a call

It seems that setting the "fr_inv_timer_avp" parameter more than once during a call is not possible. However there is a situation where this is necessary: 1. VoIP ATA to VoIP ATA call with call forwarding where call forwarded number is a PSTN destination To facilitate Call Forward No Answer, the fr_inv_timer_avp is used and set to a value (say 12 seconds), after this timer hits a failure_block is run, in this failure block i rewrite the destination and check if this destination is a PSTN number. If it is than I would like to change the fr_inv_timer_avp parameter to somthing higher due to the nature of PSTN termination but it does not seem to have any effect. Has anyone experienced this problem and possible found a workaround? Or maybe this is a known issue tavis