Need Help: Syntax Error, unexpected FUNCTION in amibroker AFL

Question

I am trying to solve this code but I am not getting what's wrong with the code. I am getting "Syntax Error, unexpected FUNCTION" This is common error but not supposed to be there and because of that error I am getting 5 more errors in the code. Check if you can solve

Here is Screenshot of errors while debugging

Here is Screenshot of errors while verifying syntax

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// Supertrend - Translated from Kolier MQ4
// see: http://kolier.li/indicator/kolier-supertrend-indi
// translation in Amibroker AFL code by E.M.Pottasch, 2011
global buffer_line_down;
global buffer_line_up;

procedure calcTrend_proc(ATR_Period,tr,ATR_Multiplier,TrendMode,CalcPrice)
{

buffer_line_down = Null;
buffer_line_up = Null;
  
PHASE_NONE = 0;
PHASE_BUY = 1;
PHASE_SELL = -1;
  
phase=PHASE_NONE;
band_upper = 0;band_lower = 0;
    
for(i = ATR_Period + 1; i < BarCount; i++)
{
    band_upper = CalcPrice[i] + ATR_Multiplier * tr[i];
    band_lower = CalcPrice[i] - ATR_Multiplier * tr[i];
      
    if(phase==PHASE_NONE)
    {
        buffer_line_up[i] = CalcPrice[i];
        buffer_line_down[i] = CalcPrice[i];
    }
    if(phase!=PHASE_BUY && Close[i]>buffer_line_down[i-1] && !IsEmpty(buffer_line_down[i-1])) 
    {
        phase = PHASE_BUY;
        buffer_line_up[i] = band_lower;
        buffer_line_up[i-1] = buffer_line_down[i-1];
    }
    if(phase!=PHASE_SELL && Close[i]<buffer_line_up[i-1] && !IsEmpty(buffer_line_up[i-1]))
    {
        phase = PHASE_SELL;
        buffer_line_down[i] = band_upper;
        buffer_line_down[i-1] = buffer_line_up[i-1];
    }   
    if(phase==PHASE_BUY && ((TrendMode==0 && !IsEmpty(buffer_line_up[i-2])) || TrendMode==1) )
    {
        if(band_lower>buffer_line_up[i-1]) 
        {
            buffer_line_up[i] = band_lower;
        }
        else
        {
            buffer_line_up[i] = buffer_line_up[i-1];
        }
    }
    if(phase==PHASE_SELL && ((TrendMode==0 && !IsEmpty(buffer_line_down[i-2])) || TrendMode==1) )
    {
        if(band_upper<buffer_line_down[i-1])
        {
            buffer_line_down[i] = band_upper;
        }
        else
        {
            buffer_line_down[i] = buffer_line_down[i-1];
        }
    }
}
}
  
SetBarsRequired(sbrAll,sbrAll);
 
TrendMode = ParamToggle("TrendMode","Off|On",1);
ATR_Multiplier = Param("ATR_Multiplier",2,0.1,10,0.1);
ATR_Period = Param( "ATR_Period",5,1,20,1);
tr = ATR(ATR_Period);
  
CalcPrice = (H+L)/2;
calcTrend_proc(ATR_Period,tr,ATR_Multiplier,TrendMode,CalcPrice);
  
SetChartOptions(0,chartShowDates);
//Plot(C,"C",colorWhite,64);

if ( TrendMode == 1 )
{
    Plot( buffer_line_up, "\ntu", ColorRGB( 28, 134, 238 ), styleThick );
    Plot( buffer_line_down, " // td", ColorRGB( 205, 51, 51 ), styleThick );


    Plot( 4, "", IIf( buffer_line_up, colorBrightGreen, colorBlack ), styleOwnScale | styleArea | styleNoLabel, -0.5, 100 );
    Plot( 6, "", IIf( buffer_line_down, colorRed, colorBlack ), styleOwnScale | styleArea | styleNoLabel, -0.5, 100 );
}