diff --git a/src/calibre/utils/ipc/simple_worker.py b/src/calibre/utils/ipc/simple_worker.py
index 5a89b91461..68d879f8a8 100644
--- a/src/calibre/utils/ipc/simple_worker.py
+++ b/src/calibre/utils/ipc/simple_worker.py
@@ -94,7 +94,7 @@ def communicate(ans, worker, listener, args, timeout=300, heartbeat=None,
 
 def fork_job(mod_name, func_name, args=(), kwargs={}, timeout=300, # seconds
         cwd=None, priority='normal', env={}, no_output=False, heartbeat=None,
-        abort=None):
+        abort=None, module_is_source_code=False):
     '''
     Run a job in a worker process. A job is simply a function that will be
     called with the supplied arguments, in the worker process.
@@ -133,6 +133,11 @@ def fork_job(mod_name, func_name, args=(), kwargs={}, timeout=300, # seconds
     :param abort: If not None, it must be an Event. As soon as abort.is_set()
     returns True, the worker process is killed. No error is raised.
 
+    :param module_is_source_code: If True, the ``mod`` is treated as python
+    source rather than a module name to import. The source is executed as a
+    module. Useful if you want to use fork_job from within a script to run some
+    dynamically generated python.
+
     :return: A dictionary with the keys result and stdout_stderr. result is the
     return value of the function (it must be picklable). stdout_stderr is the
     path to a file that contains the stdout and stderr of the worker process.
@@ -159,8 +164,9 @@ def fork_job(mod_name, func_name, args=(), kwargs={}, timeout=300, # seconds
     w = Worker(env)
     w(cwd=cwd, priority=priority)
     try:
-        communicate(ans, w, listener, (mod_name, func_name, args, kwargs),
-                timeout=timeout, heartbeat=heartbeat, abort=abort)
+        communicate(ans, w, listener, (mod_name, func_name, args, kwargs,
+            module_is_source_code), timeout=timeout, heartbeat=heartbeat,
+            abort=abort)
     finally:
         t = Thread(target=w.kill)
         t.daemon=True
@@ -174,6 +180,23 @@ def fork_job(mod_name, func_name, args=(), kwargs={}, timeout=300, # seconds
         ans['stdout_stderr'] = w.log_path
     return ans
 
+def compile_code(src):
+    import re, io
+    if not isinstance(src, unicode):
+        match = re.search(r'coding[:=]\s*([-\w.]+)', src[:200])
+        enc = match.group(1) if match else 'utf-8'
+        src = src.decode(enc)
+    # Python complains if there is a coding declaration in a unicode string
+    src = re.sub(r'^#.*coding\s*[:=]\s*([-\w.]+)', '#', src, flags=re.MULTILINE)
+    # Translate newlines to \n
+    src = io.StringIO(src, newline=None).getvalue()
+
+    namespace = {
+            'time':time, 're':re, 'os':os, 'io':io,
+    }
+    exec src in namespace
+    return namespace
+
 def main():
     # The entry point for the simple worker process
     address = cPickle.loads(unhexlify(os.environ['CALIBRE_WORKER_ADDRESS']))
@@ -185,15 +208,18 @@ def main():
             # Maybe EINTR
             args = conn.recv()
         try:
-            mod, func, args, kwargs = args
-            try:
-                mod = importlib.import_module(mod)
-            except ImportError:
-                # Load plugins incase fork_job() is being used in a plugin
-                import calibre.customize.ui as u
-                u
-                mod = importlib.import_module(mod)
-            func = getattr(mod, func)
+            mod, func, args, kwargs, module_is_source_code = args
+            if module_is_source_code:
+                importlib.import_module('calibre.customize.ui') # Load plugins
+                mod = compile_code(mod)
+                func = mod[func]
+            else:
+                try:
+                    mod = importlib.import_module(mod)
+                except ImportError:
+                    importlib.import_module('calibre.customize.ui') # Load plugins
+                    mod = importlib.import_module(mod)
+                func = getattr(mod, func)
             res = {'result':func(*args, **kwargs)}
         except:
             res = {'tb': traceback.format_exc()}