Create a trigger that moves the unit a small distance to a point towards the destination every 0.01 - 0.03 secs. Remove leaks and some arithmetic is needed for calculating the distance moved. However, this causes the moved unit to be ''literally'' stunned while the movement occurs.
For example;
Moving Unit
Events
Time - Every 0.01 seconds of game time
Conditions
Actions
Set UnitPoint = ((Position of MovedUnit) offset by 3.00 towards (Angle from (Position of (MovedUnit)) to DestinationPoint) degrees)
Unit - Move MovedUnit instantly to UnitPoint, facing (Facing of MovedUnit) degrees
Custom script: call RemoveLocation(udg_UnitPoint)
In this trigger, DestinationPoint is the destination where your unit will finally reach, UnitPoint is the point where your unit will be moved gradually towards the destination. MovedUnit is obviously the moved unit.