|You might be confusing the parser with obscure quote placement.|
cmd "C:\Program Files\QlikView\qv.exe" /r /nosecurity "D:\QlikView\Book-Bill\Book-Bill.qvw"
I would try this:
cmd "C:\Program Files\QlikView\qv.exe /r /nosecurity D:\QlikView\Book-Bill\Book-Bill.qvw"
and, with "at", I found that absolute paths are very critical, at least with win-XP. No implied or relative paths will work.