* Yellen's two-day testimony before Congress to start at 10 a.m.
* Home Depot top boost to Dow, S&P after earnings
* S&P/Case-Shiller edges higher in December
* Toll Brothers rises after results
* Indexes: Dow up 0.12 pct, S&P off 0.03 pct, Nasdaq off 0.22 pct (Adds data, updates to market open)
By Chuck Mikolajczak
NEW YORK, Feb 24 (Reuters) - U.S. stocks were flat shortly after the open on Tuesday, as the Dow and S&P 500 held near record levels before testimony by Federal Reserve Chair Janet Yellen and a flurry of economic data.
Yellen will give the central bank's semi-annual Monetary Policy Report to the Senate Banking Committee at 10 a.m. (1500 GMT), the first of her two days of testimony. Investors will attempt to parse her commentary for clues on the timing of an interest rate hike in the wake of the dovish Fed minutes released last week.
"It's a classic wait-and-see day," said Art Hogan, chief market strategist at Wunderlich Securities in New York.
"She's got a very difficult job of trying to talk Wall Street into the fact the January minutes weren't nearly as dovish as the Street interpreted them, and a June liftoff is still a credible possibility because we are data-dependent."
The S&P/Case Shiller composite index of home prices in 20 metropolitan areas gained 4.5 percent in December from the prior year above the forecast 4.3 percent rise and the 4.3 percent growth rate in November.
Home Depot shares gained 4.3 percent to $117.11 as the biggest boost to the Dow and S&P 500 after the home improvement retailer reported a better-than-expected rise in quarterly same-store sales and said it would buy back $18 billion of its shares.
The Dow Jones industrial average rose 21.35 points, or 0.12 percent, to 18,138.19, the S&P 500 lost 0.62 points, or 0.03 percent, to 2,109.04 and the Nasdaq Composite dropped 10.69 points, or 0.22 percent, to 4,950.29.
February consumer confidence along with readings on the services sectors from the Richmond and Dallas Fed are due at 10 a.m. (1500 GMT).
JPMorgan Chase climbed 2.2 percent to $60.66 after the bank said in presentations at its annual investor day that it aims to save about $1.4 billion in annual expenses by cutting costs and simplifying businesses, including an increase of about 10 percent in core loan growth in 2015.
Comcast Corp, the largest U.S. cable operator, posted fourth-quarter revenue that marginally beat estimates and boosted its buyback program to $10 billion. Its shares rose 1.7 percent to $59.18.
Toll Brothers climbed 4.1 percent to 38.62, helping to send the PHLX housing index 1.2 percent higher. The largest U.S. luxury homebuilder, reported a higher-than-expected quarterly profit and raised the low end of its full-year home delivery forecast.
Advancing issues outnumbered declining ones on the NYSE by 1,390 to 1,215, for a 1.14-to-1 ratio; on the Nasdaq, 1,117 issues rose and 992 fell, a 1.13-to-1 ratio favoring advancers.
The S&P 500 posted 33 new 52-week highs and no new lows; the Nasdaq Composite recorded 50 new highs and 7 new lows. (Reporting by Chuck Mikolajczak; Editing by Chizu Nomiyama and Nick Zieminski)