diff -r ad74e44f55d9 -r a387f258814a plcopen/plcopen.py
--- a/plcopen/plcopen.py	Fri Sep 02 18:16:58 2011 +0200
+++ b/plcopen/plcopen.py	Wed Sep 07 15:53:28 2011 +0200
@@ -649,15 +649,34 @@
     setattr(cls, "GetCustomBlockResource", GetCustomBlockResource)
 
     # Return Data Types checking for recursion
-    def GetCustomDataTypes(self, exclude = ""):
+    def GetCustomDataTypes(self, exclude = "", only_locatable = False):
         customdatatypes = []
         for customdatatype in self.getdataTypes():
-            customdatatype_name = customdatatype.getname()
-            if customdatatype_name != exclude and not self.ElementIsUsedBy(exclude, customdatatype_name):
-                customdatatypes.append(customdatatype_name)
+            if not only_locatable or self.IsLocatableType(customdatatype):
+                customdatatype_name = customdatatype.getname()
+                if customdatatype_name != exclude and not self.ElementIsUsedBy(exclude, customdatatype_name):
+                    customdatatypes.append(customdatatype_name)
         return customdatatypes
     setattr(cls, "GetCustomDataTypes", GetCustomDataTypes)
 
+    # Return if Data Type can be used for located variables
+    def IsLocatableType(self, datatype):
+        basetype_content = datatype.baseType.getcontent()
+        if basetype_content["name"] in ["enum", "struct"]:
+            return False
+        elif basetype_content["name"] == "derived":
+            base_type = self.getdataType(basetype_content["value"].getname())
+            if base_type is not None:
+                return self.IsLocatableType(base_type)
+        elif basetype_content["name"] == "array":
+            array_base_type = basetype_content["value"].baseType.getcontent()
+            if array_base_type["value"] is not None and array_base_type["name"] not in ["string", "wstring"]:
+                base_type = self.getdataType(array_base_type["value"].getname())
+                if base_type is not None:
+                    return self.IsLocatableType(base_type)
+        return True
+    setattr(cls, "IsLocatableType", IsLocatableType)
+
 cls = PLCOpenClasses.get("project_fileHeader", None)
 if cls:
     cls.singleLineAttributes = False