There's no need for scripting but you do need the right data model with the correct tables and relationships:
FloorPlan::_fkFloorPlanID = Clients::_fkFloorPlanID
You would use one method or another to assign the floor plan's record to the client record by giving the client record an ID. A number field in the Client record would record the booth # for that client.
Layout text for booth 3 on the floorplan layout can then be conditionally formatted to change fill color and text style when the following expression evaluates as True:
Not IsEmpty ( Filtervalues ( List ( Clients::BoothNumb ) ; 3 ) )
Since the same client may participate in more than one event, you may find it useful to set up a many to many relationship between floorPlan and Clients with a join table. The Booth assignment field would then be defined in the join table rather than in clients and the filter expression would be modified to refer to the Join table and it's booth number field accordingly.