Error prevention

[rfcomm2k]

I am modifying a drawing for a pole barn that was built, adding an addition to it. In doing so I discovered that there seems to be no way to prevent me from making the mistake of trying to draw a 2x6 joist right into the middle of a beam (other than common sense).
Does Acad LT 2008 have any way to let me lock an object or its boundaries so that I cannot penetrate it with another?
If not, does the full version of Autocad have this? What was the earliest version that had this feature?

[pendean]

No such tools in General-Use CAD applications like LT and AutoCAD.