I wondered if you would find Barry's thread helpful -
http://forum.alzheimers.org.uk/showthread.php?54242-Read-of-the-reality-when-Im-Sundowning
I always found my mum's sundowning difficult and I'm lucky that my husband does not really do it.
I tried to distract and go along with it but found I mostly has to ride the storm out of you see what I mean.