You may ultimately find that a set of related records is a better option than a single field with a check box set, but here's an auto-enter calculation that will automatically sort the selected values into the same order as they are listed in the value list:
FilterValues ( ValueListItems ( Get ( FileName ) ; "YourValueListNameInQuotesHere" ) ; self )
And be sure to clear the "do not replace existing values..." check box.
Thanks for the formula. It worked!