I could use some help figuring out how to develop a custom button.  We have the following Custom Objects: Marketing Campaign (very simple start / stop dates with description) and Event Attendees (which links a contact with a campaign and has checkboxes for RSVP, Confirmation, Attended).  We use this quite abit for Relating action items, email etc to campaigns.

 

We'd like to expand on this with a custom button(s) from Contact Lists to select multiple contacts from a list and then add to a campaign.  Preferably it will take user to a window to select from a campaign drop-down (similar to the way Change Lead Status works).

 

Can anyone help me get started?