Implementing security mechanism to X-WIKI App

When I open a new template in my X-WIKI app, I choose a time period to book an item and select it via a drop down menu.
In total there are 4 items as soon as on item is selected
the next person who wants to select the same item via the template during the first selected period the new person should get
an grayed-out entry in this drop down menu.
to make sure other person are unable to book the Item in the same period twice.
only if the entry is marked by the Admin the device is freely available again.

Can you help me Setting this up using X-WIKI Syntax ad Script like velocity

Thanks for your Help