minimize All MDI child windows

While trying to introduce a trivial "Windows - minimize all" function into our MDI application we faced the following problem:

the feature was implemented using loop in which each child window was minimized, something like this:

foreach (Form chform in charr)
chform.WindowState=FormWindowState.Minimized;

under Win XP this looks a little bit amusing (at first), as you can observe sequential smoothly minimization of child windows. But when the number of child windows is large enough this delay starts to irritate.

is there any way to perform minimization of all windows simultaneously?