public class NewMeeting {
    
public event ev { get; set; }
   
public NewMeeting (){
    ev = new event();
    ev.CurrencyIsoCode = UserInfo.getDefaultCurrency();
    ev.OwnerId = UserInfo.getUserId();
    ev.StartDateTime = Datetime.now().addMinutes(-Datetime.now().minute());
    ev.EndDateTime = Datetime.now().addMinutes(60-Datetime.now().minute());  
    ev.Subject = 'New Meeting';
    if ( ev.WhatId != null && ev.WhatId.getSObjectType() == Account.sObjectType )
        {
            dummyContact.AccountId = ev.WhatId;
        }
}
    
public Contact dummyContact
    {
        get
        {
            if ( dummyContact == null ) dummyContact = new Contact();
            return dummyContact;
        }
        private set;
    }
    
public List<SelectOption> contactOptions
    {
        get
        {
            if ( contactOptions == null && dummyContact.AccountId != null )
            {
                contactOptions = new List<SelectOption>();
                contactOptions.add( new SelectOption( 'null', '--None--' ) );
                for ( Contact contact :
                    [   SELECT  Id, Name
                        FROM    Contact
                        WHERE   AccountId = :dummyContact.AccountId
                    ]
                    )
                {
                    contactOptions.add( new SelectOption( contact.Id, contact.Name ) );
                }
            }
            return contactOptions;
        }
        private set;
    }

public Boolean showContactOptions
    {
        get { return contactOptions != null && contactOptions.size() > 1; }
    }
    
public String contactId { get; set; }
   
public String accountLabel
    {
        get { return Account.sObjectType.getDescribe().getLabel(); }
    }

public String contactLabel
    {
        get { return Contact.sObjectType.getDescribe().getLabel(); }
    }   
    
public void changeAccount()
    {
        ev.WhatId = dummyContact.AccountId;
        ev.WhoId = null;
        contactOptions = null;
    }

public void changeContact()
    {
        ev.WhoId =
        (   ( contactId != null && contactId != 'null' )
        ?   Id.valueOf( contactId )
       :   null
        ); 
    }        
    
public PageReference save() {
    return new ApexPages.StandardController(ev).save();
  }  

public PageReference cancel() {
    return new ApexPages.StandardController(ev).cancel();
  }     
      
}