Modifying a text file outside unity.

Hey, so I've got some code that creates a text file with some player data in it, but I can't figure out how to either:

a)modify a value in the text file, or alternatively b)delete the text file so I can rewrite it with new values.

Here's the function I'm attempting to write:

 function updatePlayerData()
 {
     Delete(docPath); //this line throws an error.
     var sr = File.CreateText(docPath); 
     for(var i=0; i< playerInfoRealArray.length; i++)
     {
          sr.WriteLine (playerInfoRealArray[i]);
     }
     Debug.Log("Updated the player's data.");
     sr.Close(); 
 }

Any idea how to do it?

Thanks!