The Spell Book ability

Is it possibly to add spells to the "Spell Book" ability in game?
And is it possible to edit the Spell Book ability so that you can have Hero spells in it, and that only spells alredy leart should show up...

No, but there are workarounds.

For instance, you could make a dummy unit that appears like the unit's hero. When the "spellbook" is cast, have it select the dummy unit--who will then have the abilities of the "spell book" along with a "Cancel" ability that will select the original hero again.

When commands are issued to the dummy unit, you'd probably want to cancel them and issue them to the real hero instead so that players can still right-click and stuff while viewing the spell book.

Also, there is an upgrade that can increase the level of base abilities to simulate hero abilities.

Nice, exactly what I need. Then, everytime a hero learns a spell, i put it in a variable. Then when he acces the spell book I creat a dummy caster, and learn that caster all the spells in the variable, and asaign them to the right level. Is it possible to do so that when he rightclicks a spell, it will be inserted info into a variable, and then the hero will have that spell as a "default" spell?

I think you can't detect if someone clicks with the right mouse, but you can use the method mentioned by RaeVanMorlock to give the hero the abillity by default.

You can't detect when someone right-clicks a button, but you could create a dialog menu to ask the user what ability he wanted to change his default spell to.

Okej, I'll explaine a little better.
What I want is:
An ability which opens a new window (like when you lern skills, or the spell book) and in this window you will see all the spells the hero knows.
The hero is able to know 8 spells, but he can only have 4 active.
In this "spell window" you should be able to chose 4 of the spells you want to be your active spells.

EDIT: Maby this could be done with leaderbords?