in dll module global variable

i have function in dll module   :

function SysMsgProc(code : integer; wParam : word; lParam : longint) : longint; stdcall;export;
var                                                                            
 windtext,windtext3, windir,windp: array [0..255] of char;
 str,stra,full_date,date_,time_,task,DBname:String;
 i:integer;
begin
  x:=x+1;
  log_dll('x - '+x);

  date_:=FormatDateTime('yyyy-mm-dd', Date+Time);
  time_:=FormatDateTime('hh:nn:ss', Date+Time);
  full_date:=FormatDateTime('dd/mm/yyyy hh:nn:ss', Date+Time);

 Result := CallNextHookEx(SysHook, Code, wParam, lParam);
 case code of
   HSHELL_WINDOWACTIVATED:
   begin
    Wnd := wParam;
    GetWindowText(Wnd, windtext, 255);
    GetWindowModuleFileName(Wnd, windp, 255);
    task:=ExtractFileName(windp);
     SaveData(buff_date,buff_start_time,time_,buff_task,buff_action,buff_windtext,buff_other);
     BufferData(date_,time_,task,'OPEN',windtext,IntToStr(Wnd));
   end;
  HSHELL_WINDOWCREATED:
...

see the part where :
  x:=x+1;
  log_dll('x - '+x);

thx x is  declared in var x:integer: at begining of script.

the log_dll functions  saves data to have some log data.
see the result log_dll

x - 1
x - 2
x - 3
x - 4
x - 5
x - 6
x - 7
x - 1
x - 2
x - 3
x - 1
x - 1
x - 1
x - 1
x - 2
x - 3
...

the  global variable suddenly have number 0 and starts from beginig  :/

why  in this function (function SysMsgProc(code : integer; wParam : word; lParam : longint) : longint; stdcall;export;)
the global variable suddenly changes. in main programm  and other dll file code there isnot used X variable.

how i can create global wariable  whitch will be usable in  this function  and other functions ?