[amibroker] plot nr7 on a indicator

[murthysuresh]

Hello
I am trying to plot a NR7- smallest range in 7 days. But i keep getting 
error. 
here is my code. can someone point where i did wrong.

rang=High-Low;
nr7=IIf(rang=LLV(rang,7),shapeDigit7,shapeNone));
PlotShapes(nr7,colorGreen);