Milton's Satan quoting Macbeth in Paradise Regained?

Johann Heinrich Füssli
Macbeth and Banquo with the Witches

(Image from Wikipedia)

In an interesting Times Online review of Anna Beer's recent book, Milton: Poet, Pamphleteer and Patriot, literary expert John Carey writes:

Some poems -- Arcades and At a Solemn Music, for example – go quite unnoticed by Beer. So does his first published poem, the sonnet on Shakespeare. Written when he was 22 and prefaced to the second folio of Shakespeare's works, it is one of the earliest tributes to his genius, and might have been expected to prompt Milton's biographer to trace the influence of Shakespeare on his art from the brilliant pastiche of Comus to Satan's despairing quotation of Macbeth at a key moment in Paradise Regained.

As readily perceived from this short selection, Carey is less than impressed by Beer's biography, but I'm not quoting it for that reason. I have a different motive.

I have not yet found "Satan's despairing quotation of Macbeth at a key moment in Paradise Regained" but wonder if a reader more literate than I might help me out here.

Does anyone know the Macbeth quote alluded to by Carey?