In rising market there shall be ample buy signals and in falling market too many sell signals.
any way,
percent=Param("percent",10,1,100,1,0);//this allows u choose increment percent
Buy=Close>((100+percent)/100)*EMA(Close,200);//where close is 10% above 200 EMA
Sell=Close<( (100-percent)/100)*EMA(Close,200);//where close is 10% bellow 200 EMA