Please any one help me to write following afl code

I want afl code for the following conditions.

One day daily candle.

Buy if value = open + 20

Sell if value = open - 20

Please help me experts to provide afl code to create buy / sell signals generate in this condition from amibroker.

For the above given condition please check below AFL

_N(Title = StrFormat("{{NAME}} - {{INTERVAL}} {{DATE}} Open %g, Hi %g, Lo %g, Close %g (%.1f%%) {{VALUES}}", O, H, L, C, SelectedValue( ROC( C, 1 ) ) ));
Plot( C, "Close", ParamColor("Color", colorDefault ), styleNoTitle | ParamStyle("Style") | GetPriceStyle() ); 

Buy = LastValue(C,1)>= Open+20;

Sell = LastValue(C,1)>= Open-20;

Thank you very much