Number Attending Event SFDC

I don't believe you can sync to SFDC campaign fields from Marketo. The only way I can kind of think of to accomplish this would be to create a custom field at the lead/contact level (let's call it RSVP_Number). In the registration flow for an event, you'd add them to the SFDC campaign and you would have a wait step (say, 10 minutes), then clear the RSVP_Number they just completed.

In that 10 minute span, you'd have a workflow rule in SFDC fire for when a lead is added to a new campaign and it would copy the RSVP_Number value from their lead/contact object into the RSVP_Number campaign custom field.

I'm not positive this would work and I've never done anything like that before, but just off the top of my head I think it might work, or at least give you some ideas of solutions.

Hmmm this is an interesting idea. Do you not need the lead information for everyone planning on attending (the unique email addresses)? I've never done this before but def interested in responses to this question. I would think you could possibly write a custom SFDC field to add these responses?

Thanks.  We don't need lead info for everyone just the primary contact for that account.

How are you planning on using the information? Don't you want to know how many actually came vs said would come? Or are you trying to compare those two (# Reg vs # Attend) in a systematic way?

We want to know how many accounts attended, not the raw number per account.  For RSVP we want to know accounts RSVP'd and the number of guests they plan to bring so, we can plan food and beverage.

We use the event check-in function more for member events not lead generation.  As a member you can bring guests with you.