I want to stop the Appointments form from opening after the WebWeekView \ WebDayView  \ WebMonthView control is double clicked and if certain conditions are met. In other words, the appointments form must only open under certain circumstances. Here is my javascript code:

//double click event of WebWeekView control:

function DoubleClick() {
    if ($get('ctl00_wpHeader_txtPolicyNumber').value == "" &

    $get('ctl00_ContentPlaceHolder1_hfItem').value == "false") {
        alert("Please select a member first.");
        //insert code to cancel opening of appointments window
    }
}