count := SendMessage(H,LVM_GETITEMCOUNT,0,0);

count := ListView_GetItemCount(H);
[Error] Unit1.pas(115): Undeclared identifier: 'ListView_GetItemCount'

uses Windows, Messages, KOL {$IF Defined(KOL_MCK)}{$ELSE}, mirror, Classes, Controls, mckCtrls, mckObjs, Graphics {$IFEND (place your units here->)};
{$ELSE}
{$I uses.inc}
 Windows, Messages, Commctrl, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 Dialogs;
{$ENDIF}
.........
procedure TForm1.Button1Click(Sender: PObj);
var count:integer;
   H:hwnd;
begin
count:=ListView_GetItemCount(H);
end;

[Error] Unit1.pas(115): Undeclared identifier: 'ListView_GetItemCount'

...
Graphics {$IFEND (place your units here->)}Commctrl;
...

SendMessage(H,LVM_GETITEMCOUNT,0,0);

ListView_GetItemCount(H);

function ListView_GetItemCount(hWnd: HWND): Integer;
begin
 Result := SendMessage(hWnd, LVM_GETITEMCOUNT, 0, 0);
end;