I believe you'll need about 2.5hours at that time. You will not encounter traffic on the way up until perhaps the M1 outside Belfast.
I have been told that there are extensive roadworks at the Park Centre roundabout at the bottom of the M1 which lead on to the Westlink and are horrendous. Best perhaps to turn off the M1 at the A55 Outer Ring junction, go up Stockman's lane and use the Malone & University Road to enter town - tho that'll be busy, but you'll be able to get parking at the rear of the city hall near the BBC (assuming that this is where your meeting is).
If you get stuck, blame the Westlink!!