I built a plugin that allows me to add people who purchase from our WP E-Commerce store to a list with custom fields for purchase date, purchase total and a few other items from the cart. This works great for new purchasers on our site, but I'd like to cycle through our existing cart database and update custom fields for all our subscribers with their purchase information.
If I go through the whole database, I will get email addresses who may not have wanted the newsletter, or who opted out before we moved to Campaign Monitor. I'd like to take an email address from CM and update the custom fields if that email also exists in our cart database. Is there an 'update only' option in the API? Or can you only 'Add' subscribers?
There is only the ability to add new subscribers, however one solution here would be to get the active subscribers from your list, get their new custom field data and update those subscribers. Using this method you will have all the data required to update your subscribers through the subscriber import