If you want them to move to the target, and then stop...

Press the key once.
And don't press it again, until they're already adjacent.
Once adjacent and stationary, spamming the key will not result in movement.

I personally spam the key, and enjoy the circling about of the target in pvp.
I've also set mine up with a toggle, so I can spam my key.
And when IWT is "on", the melee toons receive it frequently (one per press of a DPS key).
But I can turn it "off" and still spam the same key, but they don't receive the IWT.

PvP it is generally advantageous to be on, and spammed.
PvE, you'd want to press it once to move them into range and then spam or not (once they're adjacent, IWT won't cause additional movement).