Data Validation - Multiple Time Slots
 

Hi Group,

I have set up an excel sheet that is used for resource booking. The
sheet basically contains columns for: Date, Start Time, End Time.

I am trying, in vain, to put in validation so that the resource is not
booked twice for the same time slot for the same day. The Start Time
and End Time contains a drop down of time (from 0800 to 1800, in 30
mins steps) and I would like the validation to be dynamic so that when
a time slot is already booked these are not available again in the
drop-down.

Grateful for any help in achieving this.

TIA