Method Finder don`t work

var sSearchString:String;
     nStart,  nEnde : Integer;


sSearchString:= '@mymark@';


       Finder.ToStart;
       While Finder.Next(sSearchString) do
         begin
           CPPosition:= Finder.FoundPosition;
           if nStart < 0 then
             nStart := CPPosition + 1
           else
             begin
               nEnde := CPPosition;
               SetSelPosLen(nStart-1, (nEnde - nStart) + Length(sSearchString)+1);
               SelectionAsString:=' ';
               nStart := -1;
             end;
         end;
       Refresh;