How do you change the model of a specific unit using triggers

[creyzi4zb12]

Hello!! It's me again, I'm having trouble with a map I'm making.
How do you change the model of a specific unit using triggers, without replacing the unit.
Tnx in advanced!!

 

[Need_O2]

There is no such thing as I know Try morph abilities
add that ability to unit order it to use it then remove the ability