Different margins on different pages

I'm trying to apply a different topmargin on all pages except the first one. I use the following code:

procedure TfmLoFoInsert.wpLoFoMeasureTextPage(Sender: TObject;
  PageInfo: TWPMeasurePageParam);
begin
  if PageInfo.pagenr = 1 then
    PageInfo.margintop := 5725
  else
    PageInfo.margintop := 2000
end;

But when I enter the second, third and so on page the margintop stays the same (5725). What can be de cause of this problem?

:oops:

Thanks!!