Merging calendars from different employees

We currently have almost 100 employees, and the boss has a spreadsheet he uses to track employee time off plans/requests. He asks the employees to enter their own time off, but with that many employees, there is frequently a conflict with one employee having it locked for editing while others want to enter their time off (which gets much worse when one person forgets to close the file).

Is there a way to have each employee enter their own time off in a template, and then consolidate that time into a master spreadsheet? I know there are probably other applications that are better suited to this than Excel, but since it's what we use now, if I can make it work in Excel without a ton of effort (of course this is unfunded), everybody would be much happier.

Thanks in advance for any ideas.

Hi
Another way of achieving this is to have a separate worksheet within the workbook for each employee and then map each employee to a master sheet. That way an employee should only ever be updating their own sheet thereby avoiding any access conflicts.
Hope this helps.
Good luck.
Tony