Add passwords to .htpasswd files. See your web server documentation for details. See comments in each file. This will require some work on your part, but it should be straightforward. The daily schedules have the first three options.
Staff can use the calendar pages to reserve multiple days.
We also wanted our users to have passwords. We wanted to list as much information on one web browser, to reduce the need to download new pages. The vertical format allows us to list as many as 4 spectrometers on one page. Java, Java script, or VBscript were not appropriate. I also dropped all graphics and most colors, which just slow down browsers.