The Midlands club have brought in six players thus far but made their last signing back on June 21, when Spanish full-back Antonio Luna arrived from Sevilla for an undisclosed fee.
However, Lambert has refused to rule out further bolstering his squad before the window slams shut on Monday.
"We try. I don't ever stop looking at people. Whether we've got the money or not, I think it's important to always keep looking to see," he told The Birmingham Mail.
"You probably can't do what a lot of people think you can do. We try, but there wouldn't be any major movement. If something came up I thought was right and financially it was right, we'd look at it."
The Scot was also asked about the possibility of moving players on, with the likes of Stephen Ireland and Barry Bannan having yet to make a first-team appearance this season.
"It's up to other teams to make the move," he added.
"I really don't know. Until somebody picks up the phone and actually asks. I can't speak for anybody else, it's up to them whether they're interested. They know the phone number."
Aston Villa face Rotherham United in the League Cup on Wednesday.
