YAHOO [BRIEFING.COM]: The FOMC's plan for further quantitative easing caused stocks to swing dramatically this afternoon, but the broader market ultimately made a modest gain as the dollar dropped to a loss.

Action this morning was listless as participants were largely unwilling to take on positions ahead of the latest FOMC policy statement. The Fed's analysis of economic conditions was hardly changed and, as expected, it kept the target rate for the federal funds rate at 0.00% to 0.25%.

The Fed delivered to those that wanted further quantitative easing measures. It intends to purchase a further $600 billion of longer-term Treasury securities by the end of the second quarter of 2011. Those purchases will be completed at a pace of about $75 billion per month, or about $110 billion per month when taking into account the principal payments that are being reinvested from agency debt and agency mortgage-backed securities. That makes for total asset purchases of about $850 billion to $900 billion through June.

That notion caused the dollar to drop. Though it attempted to pare its loss, it still finished the day down 0.4%.

The greenback's pullback helped the major equity averages settle in higher ground with modest gains. The S&P 500 even fractionally extended its five-month high, but could not quite make it to 1200. Stocks actually had been caught up in whipsaw trade following the FOMC's statement, though the bottom line of the Fed's extra accommodative stance is supportive of stock prices.

The CRB Commodity Index climbed to a fresh two-year high earlier today, but it finished flat after it failed to sustain that move.

Oil was a primary source of support for the CRB. The energy component advanced 0.9% to settle pit trade at $84.69 per barrel, even though the latest weekly inventory report showed a bigger-than-expected build.

Natural gas prices were under pressure for the entire session. The commodity closed pit trade at $3.83 per MMBtu, down 1.0%.

Precious metals were down modestly in the early going, but dove sharply as trade progressed. Gold shed 1.4% to finish at $1337.60 per ounce and silver settled 1.6% lower at $24.44 per ounce.