If you want to fetch Max value from CRM entity record using Javascript, you can use below code, remember to change entity and field name accordingly
var authenticationHeader = GenerateAuthenticationHeader();
// Prepare the SOAP message.
var xml = “<?xml version=’1.0′ encoding=’utf-8′?>”+
“<soap:Envelope xmlns:soap=’http://schemas.xmlsoap.org/soap/envelope/'”+
” xmlns:xsi=’http://www.w3.org/2001/XMLSchema-instance'”+
” xmlns:xsd=’http://www.w3.org/2001/XMLSchema’>”+
authenticationHeader+
“<soap:Body>”+
“<RetrieveMultiple xmlns=’http://schemas.microsoft.com/crm/2007/WebServices’>”+
“<query xmlns:q1=’http://schemas.microsoft.com/crm/2006/Query'”+
” xsi:type=’q1:QueryExpression’>”+
“<q1:EntityName>EntityName</q1:EntityName>”+ //change entity name
“<q1:ColumnSet xsi:type=’q1:ColumnSet’>”+
“<q1:Attributes>”+
“<q1:Attribute>FieldName</q1:Attribute>”+ //change field name
“</q1:Attributes>”+
“</q1:ColumnSet>”+
“<q1:Orders>” +
“<q1:Order>” +
“<q1:AttributeName>FieldName</q1:AttributeName>” + //change field name
“<q1:OrderType>Descending</q1:OrderType>” +
“</q1:Order>” +
“</q1:Orders>” +
“</query>”+
“</RetrieveMultiple>”+
“</soap:Body>”+
“</soap:Envelope>”;
// Prepare the xmlHttpObject and send the request.
var xHReq = new ActiveXObject(“Msxml2.XMLHTTP”);
xHReq.Open(“POST”, “/mscrmservices/2007/CrmService.asmx”, false);
xHReq.setRequestHeader(“SOAPAction”,”http://schemas.microsoft.com/crm/2007/WebServices/RetrieveMultiple”);
xHReq.setRequestHeader(“Content-Type”, “text/xml; charset=utf-8”);
xHReq.setRequestHeader(“Content-Length”, xml.length);
xHReq.send(xml);
// Capture the result.
var resultXml = xHReq.responseXML;
// Check for errors.
var errorCount = resultXml.selectNodes(‘//error’).length;
if (errorCount != 0)
{
var msg = resultXml.selectSingleNode(‘//description’).nodeTypedValue;
alert(msg);
}
else
{
var results = resultXml.getElementsByTagName(‘BusinessEntity’);
var msg = “”;
if (results.length == 0)
{
alert(msg);
return;
}
else
{
if(results[0].selectSingleNode(‘./q1:FieldName’)!=null)
{
var MaxValue = results[0].selectSingleNode(‘./q1:FieldName’).nodeTypedValue; //change name of the field to get Max value
alert(MaxValue);
}
}}