if u know how to manage filemaker scripts and databases u could personalize ur database to suit ur needs :)
can you elaborate at all?
From what I remember of your script, that seems reasonable as the script creates the "standard" list of related records for the room type selected. The simplest fix might be to delete the record and try again. If you've enabled the delete option for the related records, this will delete them at the same time and then you can select a new room type for the new room record.
You might modify your script to check for the presence of related records and have it use Show Custom Dialog to ask for confirmation before going forward and adding more related records to what you already have. (Selecting the same room type twice by accident might create an even more confusing situation by doubling all the related records created.)