SBT:=1  ;
PH:=BBandTop(C,20,S,0.01);     
PL:=BBandBot(C,20,S,0.01); 
al:=if( SBT=1,c> PH ,h > PH ) ;  
sat:=if(SBT=1,c< PL,l< PL) ;
z:=-valuewhen(1,al-sat,al-sat);
a:=if(z=1,PL,PH);    
a