"I've got a couple of bids in for players and we'll wait and see what transpires," he told BBC Radio Leeds. "But there's no doubt we'll get four or five in, hopefully before the start of the new season."
Blackwell was very pleased by the team's 2-0 victory over Bodens BK in Sweden on Wednesday, with Michael Ricketts and trialist Brian Deane getting the goals.
"I started with eight players making their debut and I was thrilled by what I saw from them all," Blackwell added. "They all had the desire I was looking for against a team 10 games into their season and it showed in their fitness."