We’re passing a custom field value for a multi-value select-many attribute (Interest), but the new value is overwriting old values as opposed to preserving old interests and adding a new one.

EXAMPLE
————-
– List A has a multi-value select-many attribute: Interest
– user1@site.com is subscribed to List A, has previously chosen an Interest “Topic X”
– We created a special form on our site to allow users to subscribe, and we’re passing Interest: “Topic Y” using a custom field in the cf7 add-on.

WHAT’S HAPPENING: When user1@site.com subscribes using this form, their previously chosen Interest “Topic X” is removed and “Topic Y” is selected.

EXPECTED RESULT: Since the Interest attribute is select-many, the Interest attribute should retain “Topic X” and “Topic Y” should be added as an additional interest

Any ideas on how to correct this?

http://wordpress.org/extend/plugins/contact-form-7-campaignmonitor-addon/