; 000xxxxx is the FormID of the magic effect in the "A Separate Mod.esp". The first two digits should always be "00...".
MagicEffect TheMagicEffect = Game.GetFormFromFile(0x000xxxxx,"A Separate Mod.esp") As MagicEffect
If Game.GetPlayer().HasMagicEffect(TheMagicEffect)
Debug.Notification("Player has the magic effect.")
EndIf
HasMagicEffect
Note however:
(*) You may need to check for a few additional things (e.g. if the ME conditions are met etc.) for that.