Jonathan Trott made his first century of the season but Warwickshire could face a tricky final day at Horsham after Sussex closed on 204 for four and with a lead of 284 runs.
Trott hit 106 and, although he had some luck along the way, it was another step forward in his comeback after he came home early from England’s Ashes tour in the winter because of a stress-related illness.
Trott continued his superb record against Sussex with his sixth century against the south-coast county. He has also made a double hundred and five fifties, but he would not have reached three figures had it not been for some sloppy Sussex fielding.
Having been reprieved twice on the second day he was put down by Luke Wright on 97 in the over before he reached his first championship hundred since April 2012.
— Sussex CCC (@SussexCCC) July 23, 2014
Trott eventually fell on the stroke of lunch, feathering a catch to Ben Brown off the persevering Steve Magoffin, as Sussex plugged away - although their bowlers were clearly frustrated by a succession of dropped catches.
Rikki Clarke was reprieved four times in making 24 while Magoffin, who took 12 Somerset wickets on this ground last season, finished with 4-74 after taking two further wickets in the afternoon session.
Sussex began their second innings with a lead of 80 runs and batted positively in the second half of the day to extend their advantage.
They quickly lost Chris Nash in Chris Woakes’ impressive new-ball burst and there was some slow turn for Jeetan Patel to exploit before he made a further breakthrough when Luke Wells offered a return catch off a leading edge for 31.
But skipper Ed Joyce took advantage of the quick-scoring Horsham outfield with an impressive 72 off 106 balls which included 10 fours and a six over long on off Patel.
Debutant Craig Cachopa, who signed a two-year deal last week, helped him add 109 in 23 overs for the third wicket with his second half-century of the match before they both fell in the same Boyd Rankin over.
Rankin removed former Ireland team-mate Joyce for 72 when he was strangled down the leg side before Cachopa was bowled trying to carve the ball away.
Luke Wright then showed his intent by lofting Patel into the tennis courts next to the ground and he will be key to Sussex’s hopes of quick runs tomorrow prior to a declaration.
— Phil Britt (@HappeeSnapper) July 23, 2014
Trott admitted he is benefiting from time in the middle having reached triple figures for the first time this season.
He said: "It was good. It was important to spend some time in the middle. I felt pretty good at Durham last week (when he scored 50) so I just wanted to continue that and keep working and improving.
"I'm not sure that getting hundreds just to get them out of the way is the right way to phrase it. It's about going out there and being part of a team rather than just thinking about your own personal game. It's important that I maintain that mentality.
"It's important to take one step at a time. At the moment I am just concentrating on playing for Warwickshire."
Sussex skipper Joyce insists his side will be pushing for a victory on the final day.
He said: "Our position in the table means we have got to be looking upwards so we will be playing positively and trying to get a win.
"We are trying to go up the table and drawing won't really do that for us so I think we have got to dangle a bit of a carrot.
"I think 284 is quite a lot of runs already but if we can get another 100 in 14 overs that would be fantastic and put them out of the game."