Use the Manage add-ons option in the tool menu of IE. You can then search all the available plugins for IE. Not as extensive as FF, but there is still lot there. Annoyingly I could only find one language translator on there and they charge (only $20 though). Considering there are loads of free ones on FF and a fair few free websites (eg. babel fish) then is a bit of a cheek. They do have a 15 day trial though, so you can see if you really want to spend the money, or at least give you good ideas about how you want yours to work.
http://www.windowsmarketplace.com/detai ... id=2341264
Note that I'm pretty sure that some of the translation websites start translating everything you do after a certain point. So you go to the translation website (in any browser) and type in the URL you want to go to. Then it translates everything (well, not images obviously) into the language of your choice, and carries on doing it wherever you go from then on in the session.
As for the program you own then if it has a nice open API that you can access (something like XML is easy) rather than going through it's GUI then you could write your own IE plugin to use it. Manipulating the GUI automatically is possible but would be a right pain. If the program is any good then they should provide APIs. Look at
www.planet-source-code.com for a hell of a lot of great code (I've seen IE plugin stuff for example). Although with all the stuff out there that already exists and does a perfectly good job then I wouldn't really bother. I mean I have a CS degree and work as a programmer, so it wouldn't be an impossible task, but it wouldn't be worth re-inventing the wheel. Especially for $20.
Cheers