how to communicate between 2 child forms in c#.net

Hi
I've MDI form and to child forms (c#.net) and i open the 2 child opens and
in first child form what i ever i do that will be recognized in 2nd child
form.
for eg. if i clicked a button in first child form then in 2 nd child form at
that instance only it has to disply the button name which i've clicked in
Fitst child form along with some text.

Can anybody tell me how to do this task in c#.net?
Its very urgent for me
thanx in advance
Yoshitha