In-form striker Francis Green bagged a brace in front of a baying Vale Park crowd to put the Silkmen in the hat for Sunday's draw.
The live-wire striker turned neatly in the eighth minute to control a header from Martin Gritton before burying a 12-yard drive.
The Silkmen dominated the rest of the first half as Vale were outplayed in midfield. However, the home side came away after the break and in the 48th minute Louis Dodds clipped a 20-yard chip off the cross bar.
He made no mistake on 70 minutes when he was sent clear by a defence-splitting pass from Danny Glover, slotting the ball home from close range.
However, Macclesfield re-took the lead within seconds as Green pounced on an appalling back pass from Luke Prosser to score from the edge of the box.
Macclesfield sealed the game in injury time when Gritton capitalised on a slip from Griffiths to score from the edge of the box.
Manager Keith Alexander said: “It was an excellent result against a team that we’ve now beaten twice regardless of the fact that their chief scout had previously labelled us as a poor team.”
Macclesfield: Brain 8, Flynn 7, Morgan 8, Hessey 8, Brisley 7, Bell 7 (Deen 74), Dunfield 8, Brown 7, Green 9, Gritton 7, Thomas 7. (Evans 83).
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