Pistols at sunrise!
<red>DANGER WILL ROBINSON!</red>
Do not connect the solenoid anywhere close to the computer unless you understand "back EMF". You need a clamping diode across the terminals or you will have a computer sized paperweight. Learn about this issue before you implement.
Engineers. Yea, right. This ain't no pie eating contest. What you need is a physics geek.
--recomendations
-Depending on it's size, use the PP to run a relay or transistor feeding power to the solenoid.
-Use the parallel port for both in and out.
-VB is overcomplecating things unless you need to run it from a window in Windows.
-What Tom said about the spinney output, unless you have more info about it.