The 18-year-old joins the Hawks from Vanarama National League side Southend United, where he has been turning out for the Shrimpers` under-23 side.
Middlehurst, who started every Harlow game so far this season, is suffering from a pulled hamstring and is expected to be out for a minimum of four weeks.
Grossart is expected to go straight into the starting line-up for the game against Aylesbury United today.
Most clubs are looking for volunteers. Find out more on the button below:
www.PitchingInVolunteers.co.ukAll the news and results in one place.
REGISTER