IPhone : Is it possible to make a group call from an iOS App?

You can make a singular phone call from an iOS app using the following code:

NSString *phoneNumber = @"1-800-555-1212"; // dynamically assigned
NSString *phoneURLString = [NSString stringWithFormat:@"tel:%@", phoneNumber];
NSURL *phoneURL = [NSURL URLWithString:phoneURLString];
[[UIApplication sharedApplication] openURL:phoneURL];

But how would I make a "group" call?