It depends on what do you want to change in the AutoCAD drawing - if just the tabular data: an embedded OLE object will do; if text attributes: something like Excellink may help you; if the geometry (parametric drawing): some more advanced solution will be neccessary (you can also use Inventor or Revit for this)

 ok, if this is available in Revit, then where can I find a guide to learn how it is done. Example; we have diffusers in rooms in a drawing, we want to some how link that info (cfm # etc.) to a spread sheet (that can also be shown) to where if we want to we can update just the spread sheet with the new values and it will change the the diffuser (cfm # etc) automaticy or vise versa.