In order to work properly, the entity needs to have specific Save Values/Internal Variables set which tell it how long it should be moving for.

Note: This same process can be done for both position and angle.

1. You'll need to Get an existing Save Value called ltime
2. Calculate how long (in seconds) the entity will be moving before it reaches its destination.
As a simple example, this can be done via duration = distance / speed
3. Set the Save Value for m_flMoveDoneTime to the value you retrieved for ltime plus the duration calculated in step 2.
Put more simply: m_flMoveDoneTime = ltime + duration
4. Set the entity's velocity to move it to the destination at the speed used in step 2.

Once the duration of the move has elapsed, the entity will stop moving. If you have done your calculations correctly, it should stop exactly at the desired destination.