How to search a VirtualStringTree in Delphi without using Edit?

I have a VirtualStringTree with some items and want to implement in it a feature similar to what a ComboBox has.

Works like this: by pressing a certain letter it should select the first item of the grid, as I press the same letter it goes through the other items that begin with it. But if I start typing a word it should select the item corresponding to what I typed.

Ex: if I press the letter f a instead it will select the first item that starts with the letter f. If I press it three times you must select the third item that begins with the letter f.

but if I quickly type for it should select the item that starts with for, for example fornecedor

What I've been able to do so far is for it to select the item in case I press a letter, but it doesn't go through all the items as I need and doesn't even work in case I type the snippet of a word.

Follows the code that does the search:

procedure TfrmGrid.SearchForText(Sender: TBaseVirtualTree; Node: PVirtualNode; 
Data: Pointer; var Abort: Boolean);
var
  NodeData: PPonteiro;
begin
  NodeData := PPonteiro(vtvGrid.GetNodeData(Node)^);
  // Interrompe a pesquisa caso encontre um nó com o texto correspondente
  Abort := AnsiStartsText(string(data), NodeData.ITEM);
  if vtvGrid.GetFirstSelected = Node then
   Abort := False;
end;

What goes into KeyPress from VirtualStringTree:

procedure TfrmGrid.vtvGridKeyPress(Sender: TObject; var Key: Char);
var
  foundNode : PVirtualNode;
begin
  inherited;
  foundNode := vtvGrid.IterateSubtree(nil, SearchForText, Pointer(Key));

  if Assigned (foundNode) then
  begin
    vtvGrid.FocusedNode := foundNode;
    vtvGrid.Selected[foundNode] := True;
  end;
end;