In addition to using the "lockout" example program as reference, you can as well try using the following commands:
To hide a panel:
SetPanelAttribute (handle, ATTR_VISIBLE, 0);
To disable a panel:
SetPanelAttribute (handle, ATTR_DIMMED, 1);
Both of the above commands will let you disable the first panel, but they will not be able to substitute the functionality of the InstallPopup, which disables the clicking on the parent panel.