Updating Agent Job's Next Run Value
I have some code that did this; here's the relevant line:

EXECUTE msdb.dbo.sp_update_schedule @schedule_id         = @target_schedule_id
                                   ,@enabled             = 1
                                   ,@active_start_date   = @new_rundate
                                   ,@active_start_time   = @new_active_start_time


NOTE: In may case, I was updating job schedules a few days in advance, to allow a different job to run the last business day before a holiday. I seem to recall that the job scheduler may cache some data, so it's possible that doing this ten minutes before the job is supposed to run will not have the desired effect.

That said: I always double-checked that the scheduled looked right in the Job Activity Monitor after I ran my script, and they always did.