Applying Alpha Channel (In Game)

[DreamScripters]

So, by the title you can probably assume what my question will be. I know that with the castle doors in Amnesia when they take damage by an enemy a alpha channel texture will be applied to it to give it the appearance of damage (basically making certain parts of the door transparent making the appearance of the holes and cracks). Now, what I want to do is take the same logic here but apply it to when you interact with a certain entity it will make it semi-transparent. I couldn't find any methods or scripts that would allow me to simply apply a or any texture to be exact to an entity while in game. I know you can have animated material but it won't allow me to do what I want. So if you have any ideas on how I could accomplish this please reply with it, Thanks!