Help to coding unproject function

I'm coding a function to getting the coordinates of wii mote pointer in a 3D environment. I'm not sure if the code is correct or wrong because x,y coord are between -1 and 1. The code seems of gluUnProject from opengl. Someone can help me???

int Engine::unProject(float winx, float winy, float winz, Mtx44 projection, guVector *position) {
			
        guQuaternion in;
	guQuaternion out;
		
	if(guMtxInverse(projection, projection) == 0) {
		return GX_FALSE;
	}
	
	in.x = (winx - 0) / screen->getWidth();
	in.y = (winy - 0) / screen->getHeight();
	in.z = winz;
	in.w = 1.0f;

	in.x = in.x * 2.0f - 1.0f;
	in.y = in.y * 2.0f - 1.0f;
	in.z = in.z * 2.0f - 1.0f;
		
	out.x = projection[0][0] * in.x + projection[0][1] * in.x + projection[0][2] * in.x + projection[0][3] * in.x;
	out.y = projection[1][0] * in.y + projection[1][1] * in.y + projection[1][2] * in.y + projection[1][3] * in.y;
	out.z = projection[2][0] * in.z + projection[2][1] * in.z + projection[2][2] * in.z + projection[2][3] * in.z;
	out.w = projection[3][0] * in.w + projection[3][1] * in.w + projection[3][2] * in.w + projection[3][3] * in.w;
		
	if(out.w == 0.0f) {		
		return GX_FALSE;
	}
		
	out.x /= out.w;
	out.y /= out.w;
	out.z /= out.w;

	position->x = out.x;
	position->y = out.y;
	position->z = out.z;
	
	return GX_TRUE;	
}

Thanks and sorry for my bad english.