AFL to find wrong Data

Hi all,

I use Yahoo Finance as quote provider and there are a lot of wrong quotes. For example, a stock that has its price $5, next day price $120 and the next day $5 again. It is like a gap, but with a big %Change. Could someone help me with the code? I try this one, but it doesn't work:

Buy = L > ((Ref(C, -1)*2);
Sell = H < ((Ref(C, -1)*2);

Filter = (Buy OR Sell)

AddTextColumn( FullName(), "Name",100, colorDefault,colorDefault,300);
AddTextColumn( WriteIf( Buy, "Buy", "Sell" ), "Signal", 50, colorDefault,colorDefault, 50 );

SetSortColumns( 4,-5) ;

I would appreciate any kind of help.