.cpp File
...Constructor
....
void __fastcall TForm1::MyFunction(TMessage &Message)
{
ShowMessage("This is a message defined by me");
//Do my jobs
...
}
void __fastcall TForm1::Button1Click(TObject *Sender)
{
Perform(WM_MYMESSAGE,0,0);
//or ::PostMessage(Handle,WM_MYMESSAGE,0,0);
}