I would suggest using logic such as "IF [Field Name] equals [Your Desired Value], then add to campaign". If you are using a batch campaign to add users, it won't matter if the data value changes in the future.
You can also look for a data value change with a date constraint and use the old value to catch those that get overwritten.
If you are wanting to make this a recurring campaign add, you can set it to look for this value, but you'll just have to be sure to exclude existing campaign members.