Using schema validation for update

[Korol]

I have a valid xml and schema.
I put them together in javascript and generate html.
Like this:

function initAdmin() {
  var xslDoc
  strFile="Simple.Config.xml"
  strSchema="SimpleSchemaConfig.xsd";

  if (ValidateShema(strFile,strSchema)==true){
      xmlDoc = new ActiveXObject('MSXML2.DOMDocument.4.0');
      xmlDoc.async = false;

      xslDoc = new ActiveXObject('MSXML2.DOMDocument.4.0');
      xslDoc.async = false;

      AppPath = xmlDoc.url;
      xmlDoc.loadXML(xmlDoc.documentElement.transformNode(xslDoc));
      xslDoc.load("FileTree.xsl");
      folderTree.innerHTML = xmlDoc.documentElement.transformNode(xslDoc);  
}
}

function ValidateShema(strFile,strSchema){ 

try
{
       xmlDoc              = new ActiveXObject("MSXML2.DOMDocument.4.0");
       schemaCache         = new ActiveXObject("MSXML2.XMLSchemaCache.4.0");
     
       xmlDoc.async            = false;
       xmlDoc.resolveExternals = false;
       xmlDoc.validateOnParse  = false;
     
       schemaCache.add("",strSchema);
     
       xmlDoc.schemas = schemaCache;
       xmlDoc.validateOnParse = true;
       if (xmlDoc.load(strFile)) {       
         displayError("xml is valid.");
         return true;
       }
       else {
         if (xmlDoc.parseError.errorCode != 0) {
           displayError("Validation failed on " + strFile + 
                "\nReason: " + xmlDoc.parseError.reason + 
                "\nSource: " + xmlDoc.parseError.srcText + 
                "\nLine: " + xmlDoc.parseError.line + "\n");
                isValid=0;
                return false;
         }
       }
}
catch(ex)
{
     alert("Error: " + ex.message)
}
}

Everything works just fine.

User has ability to update XML data.
But when they save invalid data it will be saved.
Validation doesn’t work.
How I can validate entry every time when they try to update with the schema?
Is that actually possible? Or I have to use javascript validation.