Audio Alert

Hi all
I am trying to write AFL for NYSE Tick When Tick reading extrem level 800 to 1000 or -800 to -1000 it alert with sound but i could not figure out where i am doing wrong because it did not trigger when tick level is extrem. Plese help me find out what i am doing wrong or if some one had wrote afl for this purpose.
Thx
Manoj_SECTION_BEGIN("Price");
Ticker = ParamStr("Symbol", Name() );
PlotForeign( Ticker, Ticker, ParamColor("Color", colorCycle ), ParamStyle("Style") | GetPriceStyle() );

Plot(0,"0",colorWhite,styleThick|styleNoTitle);
Plot(400,"400",colorYellow,styleThick|styleNoTitle);
Plot(-400,"-400",colorYellow,styleThick|styleNoTitle);
Plot(800,"800",colorBrightGreen,styleThick|styleNoTitle);
Plot(-800,"-800",colorRed,styleThick|styleNoTitle);
Plot(1000,"1000",colorBrightGreen,styleThick|styleNoTitle);
Plot(-1000,"-1000",colorRed,styleThick|styleNoTitle);

_SECTION_END();


// Sound Alert
Buy = Cross ( C,800) AND Name()=="TICK-NYSE-NYSE-IND";
Sell = Cross ( C,-800) AND Name()=="TICK-NYSE-NYSE-IND";


AlertIf( Buy,"SOUND C:\Program Files\AmiBroker\Alertsound\+800ticks", "Audio alert", 2 );

AlertIf(Sell,"SOUND C:\Program Files\AmiBroker\Alertsound\-800ticks", "Audio alert", 2 );