function ValidatePlate() {
    var valid = Page_ClientValidate();
    if (document.getElementById('ctl00_ContentPlaceHolder1_txtPlate').value.length > 0)
        PlateValidated(valid);
    else
        TextBoxInvalidated();
}

function PlateValidated(valid) {
    TextBoxValidated(valid);
}

function returnFalse() {
    return false;
}

function TextBoxValidated(valid) {

    document.getElementById('ctl00_ContentPlaceHolder1_lstCategory').disabled = true;
    document.getElementById('ctl00_ContentPlaceHolder1_lstMake').disabled = true;
    document.getElementById('ctl00_ContentPlaceHolder1_lstModel').disabled = true;
    document.getElementById('ctl00_ContentPlaceHolder1_lstType').disabled = true;
    document.getElementById('ctl00_ContentPlaceHolder1_lstCategory').selectedIndex = 0;
    document.getElementById('ctl00_ContentPlaceHolder1_lstMake').selectedIndex = -1;
    document.getElementById('ctl00_ContentPlaceHolder1_lstModel').selectedIndex = -1;
    document.getElementById('ctl00_ContentPlaceHolder1_lstType').selectedIndex = -1;

    if (valid == true) {
        enableLinkButton('ctl00_ContentPlaceHolder1_btnShowAdvice');
    }
    else {
        disableLinkButton('ctl00_ContentPlaceHolder1_btnShowAdvice');
    }
}

function enableLinkButton(clientID) {
    document.getElementById(clientID).disabled = false;
    document.getElementById(clientID).disabled = "";
    document.getElementById(clientID).onclick = "";
}

function disableLinkButton(clientID) {
    document.getElementById(clientID).disabled = "disabled";
    document.getElementById(clientID).disabled = true;
    document.getElementById(clientID).onclick = returnFalse;
}

function TextBoxInvalidated() {
    document.getElementById('ctl00_ContentPlaceHolder1_lstCategory').disabled = false;
    if (document.getElementById('ctl00_ContentPlaceHolder1_lstCategory').selectedIndex > 0)
        document.getElementById('ctl00_ContentPlaceHolder1_lstMake').disabled = false;
    if (document.getElementById('ctl00_ContentPlaceHolder1_lstMake').selectedIndex > 0)
        document.getElementById('ctl00_ContentPlaceHolder1_lstModel').disabled = false;
    if (document.getElementById('ctl00_ContentPlaceHolder1_lstModel').selectedIndex > 0)
        document.getElementById('ctl00_ContentPlaceHolder1_lstType').disabled = false;
    disableLinkButton('ctl00_ContentPlaceHolder1_btnShowAdvice');
}