[amibroker] help needed for this formula

[abdulazizmr]

Dear All,
please help me to add arows (buy, sell) to this formula. for example,
when the ROCadj crosses the ROC its a buy sign and visa versa. thank you

_SECTION_BEGIN("ROCadj");
    periods = Param("Periods", 21, 2, 200, 1 );
    ROCadj = periods * EMA( ROC( C, 1 ), periods );
    Plot( ROCadj, "ROCadj "+periods, colorRed, styleThick );
    // the line below adds standard ROC overlay
    Plot( ROC( C, periods ), "ROC "+periods, colorBrightGreen );