gerg - thankfully, no. In fact, hell no.
And for exactly that reason.
Which is exactly why "wards" don't work that way. Not in canon anyway..
You're confusing the normal possible Rego effects with a Rego Ward, which is a specific, special effect, with slightly separate (and very specific) rules.
The latter is exactly how wards work by the RAW. A ward is not (as described in canon) an offensive effect - it is purely a barrier, a wall, or (yes) a forcefield - a ward against something - not an attack or counter-attack against it.
Wards, as outlined on page 114, "...use normal targets, but the target is the thing protected, rather than the thing (Form) warded against..."
The important distinction to ask is "What is the Target of the Effect that is cast?"
The Target of this ward is the tip of the lance. It's never the shield or the suit of armour - that path lies madness. (Madness I say!) 
For one, the target of the spell effect must be perceived when the spell is cast - What shield? What armour? Which is why the target of a ward is the thing to be protected against a Form. And if affecting that shield/armour with Rego to move it about, then that shield/Armour is the target, since that's what's being affected.
Worse, if the opposite ruling is made, that a Rego effect can be cast on a thing and then that thing in turn affect other things with a Rego affect... madness. See this thread for a mild example of brokeness: Spell for consideration
A force field is close enough - but a passive one, not a Star-Trek-quality "repulsor field" that bounces the object back. It just stops.
And it cannot be used to "push" the Form it wards against - combined with a bit of imagination and that too would open some huuuuge cans of worms, on several levels, both Hermetic and game-mechanic-wise.
Imagine - you "ward" a rat, to repel stone or wood for Moon duration - and then turn it loose in a castle. Fun, fun, fun. But you can't, because the rat is the target of the ward, not the stone or the wood. The casting mage can't "Rego = push" the stone/wood, as he can't perceive it - and the rat can't cast the spell that would. The rat can only be "Rego = ward = protected" from stone/wood, as per the rules for Warding on page 114.
Far, far worse, if you, as SG, were to establish the precedent that a mage can cast a spell on an object that then casts an effect on another object at a later time (as a lance tip upon a shield or armour), there is no limit (literally, if you think about it) to the complications created.
There was a thread on this that discusses this all in significantly more in depth, on "pseudo-wards", here:
Now, all that said, we start with the conclusion that a Ward 1) cannot move something, 2) cannot Rego-affect something else, and 3) only protects the target.
So...
Cast your Terram Ward on a spear tip - at the end of a very long spear. Add another, very simple Rego effect that will levitate and hold that spear tip in place in space wherever the caster concentrates - this is perfect "guidance" against anything but a larger Rego effect.
It also means that when the spear tip meets metal, it cannot push that metal, but nor will it be pushed. The metal stops at that point.
Now, while it won't "penetrate" the armour or shield, it will stop it, but not the human behind it. So the human crashes into the stopped metal at full speed. And the horse under them continues to ride forward, not being rego'd or stopped in any way but the pull of the rider behind/above it.
(And injury and possibly death follows, which gets me back to my previous incomprehension at this "past time".) 