Yes the action part is quite difficult.
An easy way would be for example:
When you press the up key, that the game orders the unit to move an X amount north (assuming you got the camera fixed on north (90 degrees)).
that trigger action would be:
That will make the unit move a small amount north:
Unit - Order <unit> to Move to ((Position of <unit>) offset by (90.00 , 0.00))
This will move the unit south:
Unit - Order <unit> to Move to ((Position of <unit>) offset by (-90.00 , 0.00))
This will move the unit east:
Unit - Order <unit> to Move to ((Position of <unit>) offset by (0.00 , 90.00))
This will move the unit west:
Unit - Order <unit> to Move to ((Position of <unit>) offset by (0.00 , -90.00))
To make him move further make the 90 a larger number.
Disadvantage of this system is that you have to press the up button again and again.