diff --git a/cpdctrl/led_script.py b/cpdctrl/led_script.py
index 320d220..37ae0ec 100644
--- a/cpdctrl/led_script.py
+++ b/cpdctrl/led_script.py
@@ -7,23 +7,48 @@ Created on Fri Jan 24 16:46:06 2025
 import time
 import re
 import numpy as np
+import watchdog
+from watchdog.observers import Observer
+from watchdog.events import LoggingEventHandler, FileSystemEventHandler
+import os
+
+class LedScriptUpdateHandler(FileSystemEventHandler):
+    def __init__(self, led_script, verbose=False):
+        super().__init__()
+        self.led_script = led_script
+        self.verbose = verbose
+    
+    def on_modified(self, event):
+        if self.verbose:
+            print("File modified: ", event.src_path)
+        filename = os.path.basename(self.led_script.filepath)
+        if os.path.basename(event.src_path) == filename:
+            try:
+                self.led_script.update()
+            except ValueError as e:
+                print(e)
+
 
 class LedScript:
-    def __init__(self, script:np.ndarray|str|int=0):
+    def __init__(self, script:np.ndarray|str|int=0, auto_update=False, verbose=False):
         """
         
 
         Parameters
         ----------
         script : np.ndarray|str|int
-            If np.ndarray: numpy array in this form:
-                [(duration, cumulative time, state), ...]
-                Where <duration> is the duration of <state>, and <cumulative duration>
+            If np.ndarray: structured numpy array with
+                dtype=[("dt", "f8"), ("dtsum", "f8"), ("led", "i4"), ("line", "i4")]
+                
+                Where <dt> is the duration of <led>, and <dtsum>
                 is the sum of all previous durations, including the current one.
+                The <line> field is the line number if the step in a script and is optional.
             If str: path to a led script file
             If int: constant led state value
         constantValue : TYPE, optional
             DESCRIPTION. The default is None.
+        auto_update: bool, optional
+            If True and script is a filepath, the script will automatically be reloaded when the file changes
 
         Returns
         -------
@@ -31,12 +56,38 @@ class LedScript:
 
         """
         self.t_start = 0   
+        self.auto_update = False
+        self.filepath = None
         if type(script) == int:  
             self.script = np.array([(0., 0., script)])
         elif type(script) == np.ndarray:
             self.script = script
         elif type(script) == str:
             self.script = LedScript.parse_script(script, ignore_errors=False)
+            self.filepath = script
+            self.auto_update = auto_update
+        if self.auto_update:
+            # event_handler = LoggingEventHandler()
+            event_handler = LedScriptUpdateHandler(self, verbose=True)
+            self.observer = Observer()
+            dirname = os.path.dirname(os.path.abspath(self.filepath)) # directory of the file
+            self.observer.schedule(event_handler, dirname)
+            self.observer.start()
+            if verbose: print(f"Led script is watching for updates on '{self.filepath}'")
+        else:
+            self.observer = None
+        self.current_dt = 0
+        assert(self.script.shape[0] > 0)
+        
+    def __del__(self):
+        self.stop()
+        
+    def stop(self):
+        print("Led script stopped watching for updates")
+        if self.observer is not None:
+            self.observer.stop()
+            self.observer.join()
+        
         
     def start(self) -> int:
         """
@@ -85,12 +136,35 @@ class LedScript:
         int
             LED Intensity [0,100]
         """
-        if self.script.shape[0] == 1:
-            return self.script[0, 2]
-        distance = self.script[:,1] - dt
+        self.current_dt = dt
+        idx = self.get_current_index(dt)
+        return int(self.script["led"][idx])
+    
+    @staticmethod    
+    def _get_current_index(script, dt:float):
+        if script.shape[0] == 1:
+            return 0
+        distance = script["dtsum"] - dt
         idx = np.where(distance >= 0, distance, np.inf).argmin()
-        return int(self.script[idx, 2])
+        return idx
+    
+    def get_current_index(self, dt:float):
+        return LedScript._get_current_index(self.script, dt)
 
+    def update(self, verbose=True):
+        print(f"Updating led script from '{self.filepath}'")
+        newscript = LedScript.parse_script(self.filepath, ignore_errors=False)
+        idx = self.get_current_index(self.current_dt)
+        # check that all past command dts are the same
+        if newscript.shape[0] <= idx:
+            raise ValueError(f"The new script is too short, it has only {newscript.shape[0]} steps but we are already at state {idx+1}")
+        if not (newscript["dt"][:idx] == self.script["dt"][:idx]).all():
+            raise ValueError(f"The new script has to match the old script until before the current state, which is step {idx+1} in line {newscript['line'][idx]}")
+        newidx = LedScript._get_current_index(newscript, self.current_dt)
+        # check that the current step dt has not shortened so much that the state should have already changed
+        if idx != newidx:
+            raise ValueError(f"The duration of the current step {idx+1} in line {newscript['line'][idx]} in the new script is too short TODO") 
+        self.script = newscript
     
     @staticmethod
     def parse_script(filepath, ignore_errors=False):
@@ -180,8 +254,8 @@ class LedScript:
             else:
                 cum_duration = states[-1][1] + duration
             # 6) append
-            states.append((duration, cum_duration, state))
-        states = np.array(states)
+            states.append((duration, cum_duration, state, i+1))
+        states = np.array(states, dtype=[("dt", "f8"), ("dtsum", "f8"), ("led", "i4"), ("line", "i4")])
         if ignore_errors:
             return states, errors
         return states