In the CS go to the the scripts list by clicking on the pencil button, second to the end of the toolbar at the top.
Click "Script"
Click "New..."
Copy and paste the quote from my previous post into the blank white area.
You may want to change the name of the script by replacing the words MyScript with something more personal to your mod.
Click the floppy disc "save" button and close the scripts window.
Go to the creatures tab, double click open the creature, the third row down says "script", next to it is a drop down box. Open it and scroll down until you find your new script.
Click it to select it, save the creature then save your mod.