who has had very successful results from a college/post graduate
school open house using radio advertising and what were the details of
this campaign?

I found this in the Old Westbury Monthly dated April 2002.
"Old Westbury held one of its most successful Admissions Open Houses
ever this Spring when more than 400 people visited campus on April 6
.... The success of the program was fueled in part by a radio
advertising campaign featuring College President Dr. Calvin O. Butts,
III.  The ads appeared on such Long Island and metropolitan New York
area stations as WCBS-AM, WALK-FM, WBAB-FM, WBLI-FM and WWRL-AM."
Old Westbury Monthly Website
http://www.oldwestbury.edu/owmonthlynewsletter/