What are the * codes to enable call forward using Line 1

[arifonline]

I want to enable unconditional call forward using star code and the call should be forwarded through Line 1. When I use *73 123456 it enables the forwarding using SP1 like SP1(123456) but I want it to forward the calls on SP2 trunk through Line 1 like LI1(123456) What custom star code I can add to star codes list? Any help will be appreciated.

[Shale]

I would try *73 ***8 123456

Maybe I am missing something, but that might do it..