Need some help in WireMod

Hi. I’m trying to create a Javelin Missile in wire mod. Basically (for those that don’t know), it’s a missile that is fired, thrusts itself straight up in the air and comes back down to hit the top of a target.

I already know how to create a homing missile, however I can’t figure out how to do the other parts very well. This is my basic idea of how to get it to work:

Part 1: Shooting up in the air
When Z-axis speed is below a certain negative value, send a positive Z value to a vector thruster

What I don’t understand:
How do I find out what the Z-axis speed of the object is? And I’m assuming I have to use an IF gate for this as well, I don’t really know how to implement one of them right.

Part 2: Detecting when the missile is high enough and then bringing it down to earth:
When World_Z is above a certain value (I don’t know the scale of the world in GMod so I don’t know what this constant should be), use a targetting device to select a player, use a beacon sensor to determine the players X,Y,Z. Send World_X minus targets World_X to the thruster yada yada yada you all know how this part works anyway.

What I don’t understand:
How do I stop the beacon from sending this information to the vector thruster until it’s at a certain height in the air? Once it’s below that height again how do I stop it from trying to shoot straight up again?

Ooo… I made one of these. I still have the dupe. Add me on steam friends… Ill be back in about oh… 8 hours from school, and then I can help you.