P245 CEEFAX 245 Thu 4 Nov 21:11/27    WALL STREET    (Middday): Blue chips were mixed by midday after a morning of volatile futures-driven dealings. "The market is trying to stablisj. $here's been a lot of program trading during the day, though it's been more cautious selling," said one trader. * US first-time jobless claims fell to 338,000 after a revised 348,000 figure last week. Factory orders were up 0.7% in September, after a revised 1.2% rise in the previous month.  World indices 243 Dow Jones 242 Euro/East Dow Jones Exchange World Ind