function IsValidMulticastGroup(
    Value: string
): Boolean;

Boolean - True when hte IP address is a multicast group address.

IsValidMulticastGroup is a Boolean function that indicates if the IP address in Value represents an IP address that is a member of a multicast group address. 

IsValidMulticastGroup returns True when the first byte of the dotted-decimal IP address is in the range identified by the constants IPMCastLo through IPMCastHi. IsValidMulticastGroup will return False when the IP address is not in the required range, or Value contains a host name instead of a dotted-decimal IP address.