modify an already defined modifier

It must be wasy but I just can’t find it !
I use blender 2.56.
I have an object with an array modifier.
I duplicate the object but I want different array parameters for the copied object.
I can’t find the way to access it !

Thank you

“I duplicated the object,” did you [Shift] + [D] to duplicate?

Yes I used shift-D.
Is it that a modifier parameters are not accessible anymore once one you the “apply” button ? I was just playing with a simple cube …and as soon as I select any object, the list modifiers used on it appears immediately as long as the “apply” button" has not been used.
Thx

When you apply a modifier, it makes the the geometry real, and removes the modifier from the list. For example if you apply a subsurf modifier, you get lots of new vertices.

Ok that settles it then. I was following a tutorial …either I missed a step or there is a mistake or whatever …
Thank you !