TREEVIEW加CHECKBOX遇Undeclared indentifier问题(30分)

在TTreeView1中加入CheckBox 代码如下:
procedure SetComCtlStyle(Ctl: TWinControl; Value: Integer; UseStyle: Boolean);
var
Style: Integer;
begin
if Ctl.HandleAllocated then
begin
Style := GetWindowLong(Ctl.Handle, GWL_STYLE);
if not UseStyle then Style := Style and not Value
else Style := Style or Value;
SetWindowLong(Ctl.Handle, GWL_STYLE, Style);
end;
end;
function IsNodeChecked(Node :TTreeNode) :Boolean;
const
TVIS_CHECKED = $2000;
var
TvItem :TTVItem; //这里 提示Undeclared indentifier 'TTVItem' 不知何故?是不是我有什么USES 或者控件 或者其他没加上去???
begin
TvItem.Mask := TVIF_STATE;
TvItem.hItem := Node.ItemId;
TreeView_GetItem(Node.TreeView.Handle, TvItem);
Result := (TvItem.State and TVIS_CHECKED) = TVIS_CHECKED;
end;

procedure SetNodeChecked(Node :TTreeNode; Checked :Boolean);
const
TVIS_CHECKED = $2000;
var
TvItem :TTVItem;
begin
FillChar(TvItem, SizeOf(TvItem), 0);
with TvItem do begin
hItem := Node.ItemId;
Mask := TVIF_STATE;
StateMask := TVIS_STATEIMAGEMASK;
if Checked then
TvItem.State :=TVIS_CHECKED
else
TvItem.State :=TVIS_CHECKED shr 1;
TreeView_SetItem(Node.TreeView.Handle, TvItem);
end;
end;

是不是要在TreeView1CustomDrawItem下写些什么???

给分吧！
procedure SetComCtlStyle(Ctl: TWinControl; Value: Integer; UseStyle: Boolean);
var
Style: Integer;
begin
if Ctl.HandleAllocated then
begin
Style := GetWindowLong(Ctl.Handle, GWL_STYLE);
if not UseStyle then Style := Style and not Value
else Style := Style or Value;
SetWindowLong(Ctl.Handle, GWL_STYLE, Style);
end;
end;

procedure TForm1.TreeView1CustomDrawItem(Sender: TCustomTreeView;
Node: TTreeNode; State: TCustomDrawState; var DefaultDraw: Boolean);
begin
SetComCtlStyle(TreeView1,TVS_CHECKBOXES,True);
end;
给分吧！

谢谢清新空气回复
运行提示 Undeclared indentifier 'TVS_CHECKBOXES'

接受答案了.