select all records in multi-select lookup

select all records in multi-select lookup

hello!
i have several forms in relationships to one another:

A. People = information about each person, including whether they receive newsletter.  have a view called "newsletter recipients" with criteria set for just those who receive newsletter.
B. Correspondence = letters from each person (bi-directional lookup to A. People) with custom response to letter to be merged into newsletter mailing, field indicating whether the custom response y/n has been merged into the mailing yet
C. Newsletter = date of newsletter, people receiving newsletter (bi-directional lookup to A. People)

Ideally, on the C. Newsletter form, I could "select all" in the multi-select lookup so that it assigns that newsletter to each recipient on the "newsletter recipient" list.  I don't know how to do that without clicking 2000+ times...
Can you please point me to a good resource?

Also, I would like to be able to bulk assign a "yes" has been included in mailing to all custom responses in Form B for all responses to date for each newsletter recipient. I could do it manually going into the B. correspondence view and bulk editing the field; other options?

Thanks so much guys!
~Reed