There's another way, which MIGHT be more efficient than constant scanning. However, I've NEVER done any benchmarking on Lite-C instructions, so I'm not sure how fast/slow (exactly) things are. The manual does give a bit of a guideline though.
What I would do is create a bounding frustrum (invisible) for the point in 3D space I want to monitor and check. That could simply be an invisible primitive (like a cube). Then I'd create an event handler for an object entering its bounds, and object leaving its bounds. The simplest way of handling the event is to set a bool true/false. However, I would take that a step further. I know I can do it in C#, but not sure if you can in Lite-C or even in 3DGS A7 at all... but, I would create a "bit flag" enumeration to get more detailed data about the state.
For example: myEnum ^= StateEnum.Entity;
Yeah, that's C#-ish, but hopefully you catch my drift. I haven't used Lite-C in ages, so I can't give a working example in it. But if these features aren't present, hopefully they shall be SOON!
Note: My example is a bit contrived; and by MY interpretation of the problem you presented. It might be a silly idea if you need to get the state of any arbitrary/random vector3 at any given time. This would just work well for a FIXED position, or one that moves infrequently. If your point will be any random vector3 in 3D space, you'd better use scanning. But if there's any way to use matrices in Lite-C/A7, that would be even better; but I think it shields you from all the underlying DirectX stuff (that I <3, heheh).