Police were called shortly before 8am after the 49-year-old victim was attacked by three masked men as he walked to his car in Palmers Field Avenue.
Three people are being questioned by police and a fourth is being hunted after the incident.
The thieves grabbed the man’s laptop and a quantity of cash and escaped in a red Citroen Picasso being driven by a woman.
The victim suffered a cut hand but was otherwise unhurt.
Officers followed the gang using cars and a helicopter along the A27 and onto the A280 Longfurlong at Patching. The offenders stopped their car and fled on foot near Clapham.
A 28-year-old man, a 26-year-old man and a 26-year-old woman, all from Oldham, Greater Manchester, were arrested on suspicion of robbery after a search was launched using patrols, the helicopter and dog teams.
The Picasso was seized and taken away to be examined.
Officers are still searching for a fourth suspect who is thin, 20 to 25-years-old with short mousey hair. He was wearing jogging bottoms with a white stripe on them and a dark t-shirt.
Anyone with information should call 101 quoting serial 0229 of 15 July or the independent charity Crimestoppers on 0800 555111.