This week, the Merseyside club welcomed two new signings in the form of Conor Coady and Amadou Onana.
Liverpool-born Coady joined the Toffees on a season-long loan from Wolves, while Onana arrived from Ligue 1 side Lille OSC for a reported fee of £30million.
Lampard believes there will be more comings ang goings at Goodison Park before the window shuts on September 1, but he refused to disclose any specific names.
The Everton boss said: "No, it would be unfair to do so. We're working away, seeing ways we can improve the squad, but until we get players in I'm only happy talking about the ones we've got in.
"But any potential targets are obviously ones for us to keep working on behind the scenes."
Everton face three injury issues ahead of this Saturday's Premier League clash with Aston Villa.
Dominic Calvert-Lewin has been ruled out for six weeks, while Yerry Mina and Ben Godfrey were both forced out of last weekend's opening day defeat to Chelsea.
"Those have contributed to our thinking," Lampard said. "We have been planning this window for a long time, since I've been here the back-end of last season.
"There's always factors you can't control; Dominic's injury last week going into the Chelsea game and two major injuries in that game.
"But we do have numbers defensively and Conor obviously came in this week, which is a big deal for us.
"So it's up to us to prioritise and keep the squad as strong as we can have it and obviously we have a bit more time to do that."
Former Toffees midfielder Idrissa Gueye has been reported to be close to a return to Goodison from Paris St Germain, while Red Bull Salzburg's Mohamed Camara and Watford's Emmanuel Dennis have also been linked with the club.
On potential outgoings, Lampard added: "Yes, that's a similar sort of answer because you have to respect the players who are still with us.
"We need to get a balanced squad and, at times, if you're bringing players in the reality is that players will leave.
"But those situations, one by one, have to be right for the club, first and foremost, and the player also and any potential club they may move to.
"So, again, I won't commit to that one until we get those things in place."