I think this may work for you:
Sys Prop, Sys Feat, Sys Sp Calls
Make a speed call number from a 3 digit number that is not in use
Make the actual # the user's mobile (91917XXXXXXX)
Go to Call Rout, Call Hand, Call Rer Always
Find a spare (Any except 1) and make Reroute for every column to the dir num being your 3 digit speed call
Remember this Always number you used
Go to Call Rer
Search the number you want to go to the mobile at night
Click change and for Night1 and Night2 make it your Rer Always number
Now when in Night Mode calls for that user will point to his mobile. Let me know if this worked. Thanks.