The usual recommendations here will be to consult a building engineer to see if the structure will support it. At least tell us exactly what you want to hang from the structure (chain hoist, rope hoist, electric hoist, etc) and whether it has a hook or what, and how much weight you intend to lift. If this is one time, and the weight is fairly limited, say 300 or 400 lbs, it might be OK to wrap a chain around the beam and hang a hoist from it, otherwise, be wary of doing anything like this.
Since you say it is sheetrocked, you are going to have to punch some holes in the sheetrock to wrap a chain or strap around it. If you are asking if its OK to lag screw an attachment to the beam, I don't think this would work.
Not sure exactly what you are trying to do.
Charles