How to depict Window Message in diagram ?

[freekiller]

I use EA to draw the outline and detail for COM component in past months.
I use component diagram usually, it is very clearly to show the interface exposed by COM.

This week I try to design a Window Control by EA,  Window Control use message to communicate with user and other Windows . thereby the message(and the notification)  is the interface of Window Control .
Should I regard every message as a single interface ?  it is cumbersome and tedious .

Any better suggestion ?

Thanks .