Help with bounding boxes?

[DiamondToaster]

For some reason, I'm unable to call cBoundingBox:IsInside(). I wanted to to something like this :

(A table object "Arena" contains a bounding box btw.)

if Arena.BoundingBox:IsInside(Player:GetPosition()) then
    -- do stuff
end

But when I call that, it says something like "given const Vector3d: expected cBoundingBox"

Ok, So I make a bounding box with the player dimensions:

local PlayerBoundingBox = cBoundingBox(Player:GetPosition(), 0.4, 1.8)
if Arena.BoundingBox:IsInside(PlayerBoundingBox) then
    -- do stuff
end

But is spits out "given [no object]: const Vector3d expected"

What am I doing wrong? Any help would be appreciated.