diff --git a/htdocs/conf/conf.php.example b/htdocs/conf/conf.php.example
index ebc3e7a9263..bdf2ca4fdf5 100644
--- a/htdocs/conf/conf.php.example
+++ b/htdocs/conf/conf.php.example
@@ -33,6 +33,24 @@ $dolibarr_main_url_root='';
 $dolibarr_main_document_root='';
 
 
+# dolibarr_main_url_root_alt
+# This parameter defines the alternative URL of your Dolibarr.
+# It must link to the external modules directory.
+# Examples:
+# $dolibarr_main_url_root_alt='/custom';
+#
+$dolibarr_main_url_root_alt='';
+
+
+# dolibarr_main_document_root_alt
+# This parameter contains absolute alternative file system directory of Dolibarr
+# Examples:
+# $dolibarr_main_document_root_alt='/var/www/dolibarr/htdocs/custom';
+# $dolibarr_main_document_root_alt='C:/My web sites/dolibarr/htdocs/custom';
+#
+$dolibarr_main_document_root_alt='';
+
+
 # dolibarr_main_data_root
 # This parameter contains absolute file system directory of Dolibarr
 # directory used to store uploaded and generated physical files.
diff --git a/htdocs/core/class/commonobject.class.php b/htdocs/core/class/commonobject.class.php
index 62de50c032b..6e60ea84b37 100644
--- a/htdocs/core/class/commonobject.class.php
+++ b/htdocs/core/class/commonobject.class.php
@@ -1386,9 +1386,27 @@ class CommonObject
 			if ($objecttype == 'invoice_supplier') { $classfile='fournisseur.facture'; $classname='FactureFournisseur';   }
             if ($objecttype == 'order_supplier')   { $classfile='fournisseur.commande'; $classname='CommandeFournisseur'; }
             //print $classfile." - ".$classpath." - ".$tplpath;
-            if(!class_exists($classname)) require(DOL_DOCUMENT_ROOT."/".$classpath."/".$classfile.".class.php");
+            if(!class_exists($classname))
+            {
+            	if (file_exists(DOL_DOCUMENT_ROOT."/".$classpath."/".$classfile.".class.php"))
+            	{
+            		require(DOL_DOCUMENT_ROOT."/".$classpath."/".$classfile.".class.php");
+            	}
+            	else
+            	{
+            		require(DOL_DOCUMENT_EXTMODULE."/".$classpath."/".$classfile.".class.php");
+            	}
+            }
 			$linkedObjectBlock = new $classname($this->db);
-			include(DOL_DOCUMENT_ROOT.'/'.$tplpath.'/tpl/linkedobjectblock.tpl.php');
+			if (file_exists(DOL_DOCUMENT_ROOT.'/'.$tplpath.'/tpl/linkedobjectblock.tpl.php'))
+			{
+				include(DOL_DOCUMENT_ROOT.'/'.$tplpath.'/tpl/linkedobjectblock.tpl.php');
+			}
+			else
+			{
+				include(DOL_DOCUMENT_EXTMODULE.'/'.$tplpath.'/tpl/linkedobjectblock.tpl.php');
+			}
+			
 			return $num;
 		}
 	}
diff --git a/htdocs/install/etape1.php b/htdocs/install/etape1.php
index ebeb7cf1b7a..c0a1e59ab3a 100644
--- a/htdocs/install/etape1.php
+++ b/htdocs/install/etape1.php
@@ -534,6 +534,12 @@ function write_conf_file($conffile)
 
 		fputs($fp, '$dolibarr_main_document_root=\''.addslashes($main_dir).'\';');
 		fputs($fp,"\n");
+		
+		fputs($fp, '$dolibarr_main_url_root_alt=\''.addslashes("/custom").'\';');
+		fputs($fp,"\n");
+		
+		fputs($fp, '$dolibarr_main_document_root_alt=\''.addslashes($main_dir."/custom").'\';');
+		fputs($fp,"\n");
 
 		fputs($fp, '$dolibarr_main_data_root=\''.addslashes($main_data_dir).'\';');
 		fputs($fp,"\n");
diff --git a/htdocs/install/inc.php b/htdocs/install/inc.php
index 478cb5d1579..61d8d1d9ec3 100644
--- a/htdocs/install/inc.php
+++ b/htdocs/install/inc.php
@@ -82,6 +82,8 @@ if (! defined('DONOTLOADCONF') && file_exists($conffile))
 		if (! empty($dolibarr_main_document_root) && ! preg_match('/^[\\/]+$/',$dolibarr_main_document_root)) $dolibarr_main_document_root=preg_replace('/[\\/]+$/','',$dolibarr_main_document_root);
 		if (! empty($dolibarr_main_url_root)      && ! preg_match('/^[\\/]+$/',$dolibarr_main_url_root))      $dolibarr_main_url_root=preg_replace('/[\\/]+$/','',$dolibarr_main_url_root);
 		if (! empty($dolibarr_main_data_root)     && ! preg_match('/^[\\/]+$/',$dolibarr_main_data_root))     $dolibarr_main_data_root=preg_replace('/[\\/]+$/','',$dolibarr_main_data_root);
+		if (! empty($dolibarr_main_document_root_alt) && ! preg_match('/^[\\/]+$/',$dolibarr_main_document_root_alt)) $dolibarr_main_document_root_alt=preg_replace('/[\\/]+$/','',$dolibarr_main_document_root_alt);
+		if (! empty($dolibarr_main_url_root_alt)      && ! preg_match('/^[\\/]+$/',$dolibarr_main_url_root_alt))      $dolibarr_main_url_root_alt=preg_replace('/[\\/]+$/','',$dolibarr_main_url_root_alt);
 
 		// Create conf object
 		if (! empty($dolibarr_main_document_root))
@@ -123,11 +125,13 @@ define('MAIN_DB_PREFIX',(isset($dolibarr_main_db_prefix)?$dolibarr_main_db_prefi
 
 define('DOL_DATA_ROOT',(isset($dolibarr_main_data_root)?$dolibarr_main_data_root:''));
 define('DOL_CLASS_PATH', 'class/');                             // Filsystem path to class dir
+define('DOL_DOCUMENT_EXTMODULE', (isset($dolibarr_main_document_root_alt)?$dolibarr_main_document_root_alt:''));	// Filesystem path to external modules dir
 define('DOL_MAIN_URL_ROOT', (isset($dolibarr_main_url_root)?$dolibarr_main_url_root:''));           // URL relative root
 $uri=preg_replace('/^http(s?):\/\//i','',constant('DOL_MAIN_URL_ROOT'));  // $uri contains url without http*
 $suburi = strstr ($uri, '/');       // $suburi contains url without domain
 if ($suburi == '/') $suburi = '';   // If $suburi is /, it is now ''
 define('DOL_URL_ROOT', $suburi);    // URL relative root ('', '/dolibarr', ...)
+define('DOL_URL_EXTMODULE', DOL_URL_ROOT.(isset($dolibarr_main_url_root_alt)?$dolibarr_main_url_root_alt:''));	// URL relative for external modules
 
 
 if (empty($conf->file->character_set_client))      	$conf->file->character_set_client="UTF-8";