I will have a trip to Canada for another purpose and it will be by car so it won't incur visa problem itself.
I thought of trying getting the multi-entry US visa as a by-product. It may be too late to book an appointment already. That is why I'd like to see their calendar first. If it takes a "full" registration to do that and the charge doesn't occur until I book it, then I will finish the registration.
Thanks!