Spells as item!?

Spells as item!?

Hi all... I'm making a map at the momement.
Now I want to add a shop into my map where you can buy spells in form of items...
Can any1 say me how I can do for example "Avatar" as item?

make items that are auto-used and triggers like
units use item ... add ability xyz to trigg. unit

Do you mean permanently adding the spell to the buying unit, or buying items that when used cast the spell?