Dear Honorable Colleague,
I agree that persistence can pay off sometimes, but where do you draw the line between being persistent and being a pest? Within the past 24 hours, I have sent 5 emails and left 2 voicemails for the Important Person you asked me to reach. I suspect IP is not responding because -- while I mention your name and indicate I am trying to make contact on your behalf -- I am an inconsequential Nobody. If IP is someone you know, wouldn't it make sense for the initial contact to come from you? You could then direct IP to me, and I could take care of the details you don't want to deal with.
Maybe I'm wrong, but if IP has been checking hir messages and voicemail, ze must surely be aware that I've been trying to get in touch regarding your event, but I'll keep trying if that's what you want. Honestly, though, I don't think this is going to go anywhere until you reach out yourself. I'm pretty sure IP's secretary, after asking my name when I called this morning, checked to see if ze was "in" first before directing me to voicemail. I'm also pretty sure IP was, in fact, in.
I hope you understand I'm not trying to to shirk my duties here. I'd really like to help you, but you might need to take the proverbial bull by the horns on this one.
P.S. It'd also be nice, when you ask me to email people inviting them to your event, if you included their last names. An email address and/or company affiliation would be optimal, but at the very least, I need last names. Otherwise, Peter, Paul, and Mary are just a bunch o' hippie communist folksinger freaks (and I'm sure you wouldn't want me inviting THEM). Thanks!