I just discovered a nifty utility in the eXpress share called wndctl.exe. You can use it to lock the keyboard and mouse prior to any install/script and unlock it later. It can also activate, minimize, maximize, restore, hide, show, flash, close, disable, enable, tile, cascade, center, move, and resize window(s).
wndctl.exe can be found in any of the following places (in x86 and x64 versions):
The syntax for wndctl.exe is:
wndctl <command> [<"window title text">] [<n>]
<command> is the command to perform, and is one of the following: