nitro & DEF: You've convinced me that I'm happy to have only a cat I'd like simply to be able to enter trades in one TWS instance for an account other than the one with which it is primarily associated. This ability appears to already be in TWS (there is a Loose Accounts section in the ini file, and an Account Number field in the order dialog that is populated by it), but it doesn't work for retail customers (at least not me). Essentially, I'd like to be able to have a single TWS instance that is used for nothing more than supporting an API link, through which I could send orders for any of my linked accounts. Is there some way to turn this ability on?