var errorMessageSet = false;
var validationCount = 0;

/*
 * Validates the contact details entered by the user.
 */
function validateContactDetails(sender, args)
{
    validationCount++;

    var email = document.getElementById("emailAddress").value;
    var telephone = document.getElementById("telephoneNumber").value;
    
    args.IsValid = email != "" || telephone != "";
    
    if(!args.IsValid && !errorMessageSet)
    {
        sender.errormessage = "Please enter either a telephone number or an email address";
        errorMessageSet = true;
    }
    else
    {
        sender.errormessage = "";
    }
    
    if(validationCount == 2)
    {
        //Reset it for next time round
        errorMessageSet = false;
        validationCount = 0;
    }
}