I was playing with that a little and I'm not sure it will work. The problem is that I can only set the aim point out to 2AU and I'm looking to run the closest approach of the stars at about 30 AU. I think I have a way to do it, but I'm going to have to experiment.
Unfortunately, if you want a really far out nearest approach like that, you're either going to have to set a higher velocity than if you wanted a very close approach, or you'll have to aim much further than the sun than you actually want it to go, because it will dramatically curve toward the sun as it goes past, especially the star being near the mass of our own sun, and if you don't set the velocity high enough (which what logically seems "high enough" usually actually isn't) there's a strong chance that the star will fall into a binary system with our sun and the other star in highly elliptical orbits, which basically means if you leave the simulation going for more than a few hundreds or, if the effect is bad enough, tens of years, there won't be any stable orbits to speak of when you come back to it. Also, I'd say that any planet within 5-10 AU of the other star's passing have almost no chance of staying in the sun's gravitational grip; they'll be slingshotted out very easily, and if a planet comes within about 4 AU it pretty much has no chance.
About the "only able to set the aim point to 2 AU", depending on what you mean, I may or may not be able to help you.
Also, a lot of this applies no matter what, but some of it I'm not too sure about since you're using the encounters tab, and I don't know if that actually considers how much the sun will pull on the other star and vice versa, but if it does consider that then a lot of this post can be ignored, I just don't know for sure, since I don't use the encounters creator much, if I want to do that sort of thing I usually do it manually so that it's more natural (aka the angle it comes in from isn't 10.00 degrees, it might be 11.483 or something, but the chances of such an event is extremely rare (on its own is still rare especially with how spread out and slow moving the stars around the sun are, but having a specific angle like that is much less likely since there are many more possibilities that aren't a regular number) but if you're looking for extreme accuracy, I suppose having the angle and other parameters set exactly will make it more so.