I'm not sure that I've ever seen a MSFL formula for SAR... I know it can be done as an MSX in C++. There is already some work published on this. Google it for more info.

Here is the metaquote code for Parabolic SAR ... Hope this helps [code:1:d6482b5d5f]//+------------------------------------------------------------------+ //| Parabolic.mq4 | //| Copyright © 2004, MetaQuotes Software Corp. | //| http://www.metaquotes.net/ | //+------------------------------------------------------------------+ #property copyright "Copyright © 2004, MetaQuotes Software Corp." #property link "http://www.metaquotes.net/" #property indicator_chart_window #property indicator_buffers 1 #property indicator_color1 Lime //---- input parameters extern double Step=0.02; extern double Maximum=0.2; //---- buffers double SarBuffer[]; //---- int save_lastreverse; bool save_dirlong; double save_start; double save_last_high; double save_last_low; double save_ep; double save_sar; //+------------------------------------------------------------------+ //| Custom indicator initialization function | //+------------------------------------------------------------------+ int init() { //---- indicators IndicatorDigits(Digits); SetIndexStyle(0,DRAW_ARROW); SetIndexArrow(0,159); SetIndexBuffer(0,SarBuffer); //---- return(0); } //+------------------------------------------------------------------+ //| | //+------------------------------------------------------------------+ void SaveLastReverse(int last,int dir,double start,double low,double high,double ep,double sar) { save_lastreverse=last; save_dirlong=dir; save_start=start; save_last_low=low; save_last_high=high; save_ep=ep; save_sar=sar; } //+------------------------------------------------------------------+ //| Parabolic Sell And Reverse system | //+------------------------------------------------------------------+ int start() { static bool first=true; bool dirlong; double start,last_high,last_low; double ep,sar,price_low,price_high,price; int i,counted_bars=IndicatorCounted(); //---- if(Bars<3) return(0); //---- initial settings i=Bars-2; if(counted_bars==0 || first) { first=false; dirlong=true; start=Step; last_high=-10000000.0; last_low=10000000.0; while(i>0) { save_lastreverse=i; price_low=Low[i]; if(last_low>price_low) last_low=price_low; price_high=High[i]; if(last_high<price_high) last_high=price_high; if(price_high>High[i+1] && price_low>Low[i+1]) break; if(price_high<High[i+1] && price_low<Low[i+1]) { dirlong=false; break; } i--; } //---- initial zero int k=i; while(k<Bars) { SarBuffer[k]=0.0; k++; } //---- check further if(dirlong) { SarBuffer[i]=Low[i+1]; ep=High[i]; } else { SarBuffer[i]=High[i+1]; ep=Low[i]; } i--; } else { i=save_lastreverse+1; start=save_start; dirlong=save_dirlong; last_high=save_last_high; last_low=save_last_low; ep=save_ep; sar=save_sar; } //---- while(i>=0) { price_low=Low[i]; price_high=High[i]; //--- check for reverse if(dirlong && price_low<SarBuffer[i+1]) { SaveLastReverse(i,true,start,price_low,last_high,ep,sar); start=Step; dirlong=false; ep=price_low; last_low=price_low; SarBuffer[i]=last_high; i--; continue; } if(!dirlong && price_high>SarBuffer[i+1]) { SaveLastReverse(i,false,start,last_low,price_high,ep,sar); start=Step; dirlong=true; ep=price_high; last_high=price_high; SarBuffer[i]=last_low; i--; continue; } //--- price=SarBuffer[i+1]; sar=price+start*(ep-price); if(dirlong) { if(ep<price_high && (start+Step)<=Maximum) start+=Step; if(price_high<High[i+1] && i==Bars-2) sar=SarBuffer[i+1]; price=Low[i+1]; if(sar>price) sar=price; price=Low[i+2]; if(sar>price) sar=price; if(sar>price_low) { SaveLastReverse(i,true,start,price_low,last_high,ep,sar); start=Step; dirlong=false; ep=price_low; last_low=price_low; SarBuffer[i]=last_high; i--; continue; } if(ep<price_high) { last_high=price_high; ep=price_high; } } else { if(ep>price_low && (start+Step)<=Maximum) start+=Step; if(price_low<Low[i+1] && i==Bars-2) sar=SarBuffer[i+1]; price=High[i+1]; if(sar<price) sar=price; price=High[i+2]; if(sar<price) sar=price; if(sar<price_high) { SaveLastReverse(i,false,start,last_low,price_high,ep,sar); start=Step; dirlong=true; ep=price_high; last_high=price_high; SarBuffer[i]=last_low; i--; continue; } if(ep>price_low) { last_low=price_low; ep=price_low; } } SarBuffer[i]=sar; i--; } // sar=SarBuffer[0]; // price=iSAR(NULL,0,Step,Maximum,0); // if(sar!=price) Print("custom=",sar," SAR=",price," counted=",counted_bars); // if(sar==price) Print("custom=",sar," SAR=",price," counted=",counted_bars); //---- return(0); } //+------------------------------------------------------------------+[/code:1:d6482b5d5f]

Here are some more resources: http://tadoc.org/indicator/SAR.htm