Hi Mark,
You can accomplish this by creating three Additional Extensions for the receptionist. Then associate each Additional Extension to the hunt group with the appropriate Manager. Thus Additional Extension #1 will ring when Manager #1 Hunt group is called, Additional Extension #2 will ring when manager #2 Hunt Group dialed...
The only caveat is that the receptionist must have a phone model such as a SPA508G or SPA509G that will accomodate the extra line buttons along with any other functions used by receptionist.
Cheers,
Julio