diff --git a/src/nlac/NLSClientScript.php b/src/nlac/NLSClientScript.php
index 8643f19..4e20b40 100644
--- a/src/nlac/NLSClientScript.php
+++ b/src/nlac/NLSClientScript.php
@@ -145,6 +145,7 @@ class NLSClientScript extends \CClientScript {
 /**
  * @param string $appVersion
  * Optional, version of the application.
+ * Set 'auto' will allow auto regenerate when source changed
  * If set to not empty, will be appended to the merged js/css urls (helps to handle cached resources).
  **/
 	public $appVersion = '';
@@ -188,10 +189,16 @@ class NLSClientScript extends \CClientScript {
 	protected $cssMerger = null;
 	
 	
+	protected $isAutoAppVersion = false;
 	
 	public function init() {
 		parent::init();
 		
+		if ($this->appVersion == 'auto'){
+			$this->isAutoAppVersion = true;
+			$this->appVersion = 0;
+		}
+		
 		if (is_numeric($this->nlsScriptPosition))
 			//-> we need jquery
 			$this->registerCoreScript('jquery');
@@ -224,6 +231,14 @@ public function init() {
 	}
 	
 	protected function addAppVersion($url) {
+		// if auto version flag is set (appVersion='auto')
+		// get file modified time and use as version before hashing
+		if ($this->isAutoAppVersion && !NLSUtils::isAbsoluteUrl($url)) {
+			$ver = NLSUtils::getFileMTime($url);
+			$this->appVersion = max($this->appVersion, $ver);
+			return NLSUtils::addUrlParams($url, array('nlsver' => $ver));
+		}
+		// original none auto
 		if (!empty($this->appVersion) && !NLSUtils::isAbsoluteUrl($url))
 			$url = NLSUtils::addUrlParams($url, array('nlsver' => $this->appVersion));
 		return $url;
@@ -478,4 +493,5 @@ protected function _putnlscode() {
 
 		$this->registerScript('fixDuplicateResources', $js, $this->nlsScriptPosition);
 	}
-}
\ No newline at end of file
+	
+}
diff --git a/src/nlac/NLSUtils.php b/src/nlac/NLSUtils.php
index adeb70d..1b36254 100644
--- a/src/nlac/NLSUtils.php
+++ b/src/nlac/NLSUtils.php
@@ -19,5 +19,11 @@ public static function addUrlParams($url, $params) {
 	public static function isAbsoluteUrl($url) {
 		return preg_match('@^https?://@', $url);
 	}
+	
+	public static function getFileMTime($path){
+		// append doc root and remove trailing
+		$path = $_SERVER['DOCUMENT_ROOT'].preg_replace('@[\?#].*$@', '', $path);
+		return file_exists($path) ? filemtime($path) : 0;
+	}
 
-}
\ No newline at end of file
+}