3D - Working out x,y,z coordinates

I am working on a function that will convert a theoretical 3d point into x and y coordinates on the screen. But I need to know where the 3d point is in relation to the camera.

My question is: How would I work out the position of a theoretical 3d point in relation to the camera’s x, y and z coordinates and the cameras pitch, roll and yaw?

It would be in the form of a function like this:

convert3Dto2D = function(pointIn3D:Object) {
     //pointIn3D has x, y and z variables
     3d.x = ????? //this is the x in relation to the camera
     3d.y = ????? //this is the y in relation to the camera
     3d.z = ????? //this is the z in relation to the camera
     2d.x = //This section I already know but it needs 3d's x, y and z
     2d.y = //This section I already know but it needs 3d's x, y and z
     return 2d
}

I am using flash 8 by the way.