Unless you can provide some more information about what you have tried so
far, or at least about your level of knowledge and experience with Access,
your question is a very general outline from which to request volunteer help
to devise a system for managing employee vacations.  A Google group search
may turn up some discussion on the subject, and lead you to a sample
database that can be adapted for your purposes.  If that doesn't lead
anywhere you will need to do some research about how to build a database.
The following links may help in that search:
http://www.mvps.org/access/
http://allenbrowne.com/tips.html
http://allenbrowne.com/links.html

There are some templates at Microsoft, one of which can perhaps be adapted,
or at least help to point you in the right direction.
http://office.microsoft.com/en-us/templates/CT101527321033.aspx?av=ZAC