how to send messages between diferents dialogs?

Hello, in my aplication there are two dialogs CCalibracionDlg and DlgMap1 both derived from Cdialog, when I press a button in DlgMap1 i have to send a message to CCalibracionDlg, how can i do this?
I've been trying to do this with PostMessage(hWnd, WM_MYCUSTOMMESSAGE,(WPARAM) wParam,(LPARAM) lParam ); or SendMessage , but in DlgMap1 how can i get the hWnd to CCalibracionDlg?
Thanks in advance.

It depends on your project and it's really hard to say how without seeing some of your code.
For example you can save the CCalibracionDlg window's handle as a member in DlgMap1 class.