Ok, you asked if you can, I answered you can.
Now you ask how? I answer "call SetUnitAnimationByIndex(udg_tempUnit, 2)"
Of course, you must first store unit in variable like tempUnit which is used in this example.
Secondly, you must know which number is for walk animation, usually first animation in the left panel of WE has number 0, second is 1 etc etc.
And I strongly recommend to make this custom script sticky somewhere in trigger section. It is usefull