Much to your surprise, the old Invisiblity Task Force office and the Experimental Charms office are completely empty. Where did everyone go?
Never fear, as a new door has sprung up a few feet away. A shiny new nameplate is posted to the door reading:
The two offices have now joined into one. There are many more desks than your average office to accomadate all the employees.
The responsibility of the Invisibility Task Force is to magically conceal things (such as buildings and other areas of importance) from the Muggle eyes. One example of the Force's work would be the powerful charm that hides Hogwarts School of Witchcraft and Wizardry from Muggle view. They are also in charge of upkeeping the protective enchantments on this level.
As for the Experimental Charms Office, this committee is in charge of handling any experiments that wizards and witches conduct using spellwork. If someone presents a new spell that they "invented" to the committee, it is their job to determine whether or not the new spell is dangerous or not, and whether it should be registered. Also, if any reports of dangerous experiements come in, the committee should take care of the situation IMMEDIATELY. If you have some free time, it is all encouraged that you dabble in experimentation yourself to come up with some new charmed objects for us!
All employees in these two offices may work together on plots for BOTH offices.