A SOCCER ball has never yet graced the pitch at Croke Park. But one of the top money men in British soccer will enter the hallowed portals next week and make it at least as far as the Football Bar. Danny McGreitor. commercial manager of Manchester United, will speak at a seminar on Business in Sport organised by the Marketing Institute. The other speakers include Title editor Cathal Dervan and Dermot Power, marketing manager of Croke Park.