// If there is only one button, you can do something like:
WebBrowser1.OleObject.Document.forms.item(0).elements.item(0).click;
// This will do a click on the first element of the first <FORM>, where an
// element is either <INPUT>, <SELECT> or <TEXTAREA>.

// If there is more than one button, you can do something like:
procedure TForm1.Button1Click(Sender: TObject);
var
 ovElements: OleVariant;
 i: Integer;
begin
 ovElements := WebBrowser1.OleObject.Document.forms.item(0).elements;
 for i := 0 to (ovElements.Length - 1) do
  if (ovElements.item(i).tagName = 'INPUT') and
  (ovElements.item(i).type = 'SUBMIT') and
  (ovElements.item(i).Value = 'Recent Charges') then
  ovElements.item(i).Click;
end;