putting objects on the screen

[jargon]

farshizzo-
I guess I only have 1 object- it's a tennis court - but really it's just the net that I want to obstruct the ball. And only some of the time (when it's on my side of the court I want the ball to appear in front of the net; however on my opponent's side I want the ball to appear behind the net). If it's impossible I'll formulate another strategy
thx,
jargon