procedure TIB_CustomVTree.DoInitNode(Parent, Node: PVirtualNode; var
InitStates: TVirtualNodeInitStates);
.........
i := Header.Columns.Count;
SetLength(NodeData.ColumnText, Header.Columns.Count);
For ii := 0 to i - 1 do
begin
j := Header.Columns[ii].Tag; ------>>> here is the problem

undeclared identifier Tag ,i searched the header but where it is declared ??