I am wondering if there is any good realtime charting software that will plot the spread of two instruments as if they were a single entity as well as give you the option to change the ratio between the two so as to keep the spread as close to zero as possible (for obvious reasons)? I have checked out Ensign, Ninja and Sierra and from what I can tell, none of them offer what I am looking for. I have an account with IB right now, so I have a data feed if whatever charting software is compatible with them? Thanks so much for any help and have a great year trading!!