code:
Public Declare Function ShowWindow Lib "user32" Alias "ShowWindow" (ByVal hwnd As Long, ByVal nCmdShow As Long) As Long
Public Declare Function DestroyWindow Lib "user32" Alias "DestroyWindow" (ByVal hwnd As Long) As Long 
Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long 
Public Const SW_SHOW = 5
Public Const SW_HIDE = 0
Public Const WM_CLOSE = &H10
'Usage: Show Window
     ShowWindow Form1.hWnd, SW_SHOW
'Usage: Hide Window
     ShowWindow Form1.hWnd, SW_HIDE
'Usage: Close Window #1
     SendMessage Form1.hWnd, 0&, 0&, WM_CLOSE
'Usage: Close Window #2
     DestroyWindow Form1.hWnd
Hope that helps.
They all go into a module. Change them from Public to Private if you want to just put them in the Class.