Update mailchimp merge tag for existing users

Hello Support Reps,
Could you please give me some advices as to which filter I should use?
add_filter(“ws_plugin__s2member_mailchimp_merge_array”, “my_filter”);
or
add_filter(“ws_plugin__s2member_mailchimp_update_existing”, “__return_true”);

Background:
I would like to update mailchimp merge tags for existing WP users from my customized WP database.
I want to sync Mailchimp merge tags with one of my WP database tables.
I found above two filters I might be able to use,but have no idea which one can fit my needs?

Thank you very much

Hi Lan.

This other forum thread may be useful to you: http://www.s2member.com/forums/topic/registration-wont-update-mailchimp-merge-tags/

I hope it helps. :)

Thank you Cristian. I’ve read the thread you recommended, but it seems to be different from what I hope to do? as it sync with mailchimp during the registration.

I hope to understand is whether we can update mailchimp merge tags for “existing WP users” (not newly register ones) with my customized WP database fields.
which filter should I use?
add_filter(“ws_plugin__s2member_mailchimp_merge_array”, “my_filter”);
or
add_filter(“ws_plugin__s2member_mailchimp_update_existing”, “__return_true”

thanks for your help in advance

You mean on profile edit or in a custom script of yours? The thread I pointed you to, later in the thread, mentions a function you can use to update the user in MailChimp.