Random hypothetical situation. Let's say I place an order for 200,000 shares of Noront at a buy limit of 45 cents (ignore the fact that I don't think I've ever placed a single order for more than $60k). I use Scotia iTrade for orders, and when I place an order, the "good until" limit is about four weeks out.

My 45 cent buy order gets in a lineup with all other orders at 45 cents. So people who placed buys at 45 cents are ahead of me in line, and people who place orders at 45 cents after me are behind me in line. Ignoring the impact of "market" orders and "all or none" orders, it's a simple seniority system.

Let's say that on today's date, August 11th, I am at the last day of an outstanding order that I placed approximately four weeks ago. I go in to "modify" the existing order, rather than cancelling it and placing a new order for the same amount.

Question: Does my order stay at the same place in the lineup, since it's a modification of an existing order? Or do I go back to the back of the line?

I'd appreciate hearing feedback from anyone who has definitive knowledge of how this is treated, rather than just an educated guess. I'd be tempted to call the Scotia iTrade help line to ask, but they'd put me on hold for 25 minutes and probably give me the wrong answer.