Using 2 internet conection on one PC

I am sure someone will be thinking "not another one". I have seen several post in these forums about doing this but most just want faster speed, a few had some unique twists but nothing that seemed usable for what I need. What is almost depressing is those that want faster speeds have more speed on one connection than I can get on both of my connections. I can't fathom why one would need that much speed, but I digress.

In my case I live way, way out in the country, no cable, no DSL, I am stuck with satellite and tethering my smart phone. Now one might think the smart phone could solve it all, and true I have seen maintained speeds of 1600K with spikes over 2400K (saw almost 3000K once). Unfortunately those kinds of speeds are only reached in the very late evening and earlier morning hours (or if I am in town). During the day, while every once in a great while for a second it may hit those speeds, getting it to even give me an average 100K consistently, is a fantasy.

Now, I also have satellite for my internet. And it speeds are decent for most things (on occation it get a bit slow), but they have this off the wall policy they call a fair usage policy (very dumb name for the policy). Basically if I use over 3GB of bandwidth (cost about $90/month) in a rolling 30 day window (not per month) they knock my speed back to about 80K till my usage for the rolling 30 day window is under 75% of my 3GB allowance. Basically I do not dare watch any videos or download anything more than a few MB in size, or I could end up stuck at horrendous speeds for a week or so.

So to make this all work I only do large downloads and watch videos using my phone. Usually I do downloads while I am sleeping, and if I wish to watch a movie, I have to do it late. But every once in while I will want to start a download at say 10am because its a fairly good chance it will be done before it gets to late. Or on occasion I have had large enough downloads that it takes longer than what I plan to be asleep for. So doing this means I have no, usable, internet access during the download. I have on several occasions tried enabling the satellite while a download on my phone was in progress but any attempts to access a web page would still go through my phones connection. Well today I found I needed a 200MB download and waiting on my phone was not an option (plus 200MB won't impact me too much) so I ran it on the satellite but while it was going I connected my phone and found all web site requests went through my phone, also a small update was found and it downloaded via the phone, all while the 200MB download continued on the satellite connection.

So the question, is there a way that I can direct what connection is used? No matter what is connecting; IE, Firefox, Windows Update, Online Game, etc can I tell them which connection to use? I am not looking for load balancing, just to point a given activity to use a particular connection while simultaneously pointing another activity to use a different connection. So, for example, if I need a download I can use IE via the smart phone to download, while I use Firefox via the satellite to continue working.