When the user clicks on an iconized (minimized) form in the taskbar, Windows sends that form a WM_QUERYOPEN message, and inspects the value returned to the operating system. If this value is zero, the operation is canceled.

Using subclassing you can therefore determine when a form is about to be restored, and you can also refuse to restore it by returning 0. Here is a code snippet that does the trick:

' REQUIRES THE MSGHOOK.DLL COMPONENT'' you can omit the following constant definition, ' because it is contained in the MsgHook type libraryConst WM_QUERYOPEN = &H13Dim WithEvents FormHook As MsgHookPrivate Sub Form_Load()    ' start form subclassing     Set FormHook = New MsgHook    FormHook.StartSubclass hWndEnd SubPrivate Sub FormHook_AfterMessage(ByVal uMsg As Long, ByVal wParam As Long, _    ByVal lParam As Long, retValue As Long)    If uMsg = WM_QUERYOPEN Then        ' The iconized form is being restored.        ' ...        ' Uncomment the next line to prevent the window from being restored.        ' retValue = False    End IfEnd Sub