trajectory

I have a radius of attack, that will trigger when an enemy enters. I fire a missile at the target position (a point to point style attack). My problem is that I need the missile to continue past that position until it reaches the range of attack. How would I accomplish this?

//The ability is within the attack range radius
				if (abilityDistance < myCollider.radius)
				{
					//Directional Ability movement
					float step = abilitySpeed * Time.deltaTime;
					theCurrentAbility.transform.position = Vector3.MoveTowards(theCurrentAbility.transform.position, targetPosition, step);
					theCurrentAbility.transform.LookAt(targetPosition);
				}

if (myAttackWho == AttackWho.AttackStrongest)
					{
						targetPosition = new Vector3( strongest.transform.position.x, this.transform.position.y, strongest.transform.position.z);
					}

wow, it was so easy

theCurrentAbility.transform.position += Vector3.Forward * step