The phrase "at a different event" is correct and usable in written English.
It can be used to refer to an occasion or gathering that is separate from the one currently being discussed.
Example: "I met her at a different event last month, where we had a chance to talk about our projects."
Alternatives: "at another occasion" or "during a separate gathering".
An image of Frederick smiling meekly at a different event was circulated on Twitter, with the implication that this had been his demeanor during the visit to the White House.
Groups such as Oxfam and WWF were evidently at a different event.
The company holds multiple pitch days throughout the year, each one held at a different event and focused on a different sector or field.
Petersen backed out of a speaking gig at a conference, telling them that one of his kids was sick, then proceeded to party at a different event (while Plazes told the world).
Though she's shown above at a different event on Thursday, Anderson debuted the new 'do on Tuesday, according to People.
She did indeed look stunning that night, but I wish she had shown off her outfit and beauty at a different event.
Having showed his prowess in long distance races, Hunter had his eyes on a different event at the 121st running of the Penn Relays.
A node u of G can be mapped on such a vertex x according to different scenarios, each postulating a different event at node u among those of Definition 1.
Williams' office has been in touch to say she was not in the audience for Hamlet, and had been at the Barbican that day for a different event, a recital by the pianist Stephen Hough.
This seminar aims to bring forth more comprehensive, complex and holistic understandings of material and materiality which varies in impact at different event scales from personal to communal and local to global.
Isella and co have examined data taken from RFID cards that recorded the interactions between people at two different events: an exhibition at the Science Gallery, a museum in Dublin, and a conference at the Institute for Scientific Interchange Foundation in Italy.
