The former Leyton Orient, Sheffield Wednesday, Nottingham Forest and Charlton man agreed a deal with Blackwell two weeks ago and is set to join on a free. Bart-Williams was born on 16 June 1974 in Sierra Leone and was loaned out to Ipswich last year.
Blackwell needs midfield backup after losing Eirik Bakke with a cruciate ligament injury. He said: "We are desperately short of midfield players. That is not what I want at the moment and I need to bring people in."
Blackwell is also hoping to pull off a deal for former Arsenal goalkeeper Rami Shabaan.