Noob(er) Question

Hi everyone! I'm quite new at modding Baldur's Gate, and I am stuck on a certain problem. I am trying to create a spell that "unmemorizes" one instance of another spell from the spellbook. Essentially, I am trying to do what either RemoveSpell or RemoveSpellRES would achieve, but inside of a spell instead of a script. Does anyone know if this is possible from a spell effect? I've personally tried "Remove Spell (172)," but that completely removes the spell from the spellbook, not just one memorized instance.