What error is in my code? I want to get a notification when the price closes first below the lower bolliger line after it closes above

[vokta]

double a=iBands(NULL, 0,20,2,0,MODE_LOW,1,1)

double b=iBands(NULL, 0,20,2,0,MODE_LOW,1,2)

if (iClose(NULL, 0,1)>a&&iClose(NULL, 0,2)<b)

[lippmaje]

double a=iBands(NULL, 0,20,2,0,PRICE_CLOSE,MODE_LOW,1);
double b=iBands(NULL, 0,20,2,0,PRICE_CLOSE,MODE_LOW,2);

if (iClose(NULL, 0,1)>a&&iClose(NULL, 0,2)<b)

b : 2nd last   a : last bar