Thanks!
Cheryl
Maybe the first thing to be aware here is that, there is no "one shoe fits all" solution out there. If there is indeed anything, you or someone may need to "modify" whatever you find to suit or meet requirements.
Second - php + calender in google may yield some useful results.
Third - IMHO + FWIW - of the many calendars I have reviewed just recently, Webcalendar was one of the better ones. It's a pretty powerful and well documented multiuser web based calender. You would need to modify it to suit your needs though. HTH