Aye,
When creating a new component, in the component properties window, check the "Units are not interchangeable" option.
Say on unit A you draw a rectangle, and add a few pins, then go to unit B, the rectangle remains but the pins are no longer there, allowing you add different pins.
Now, say you wanted to make a new rectangle, and not have the one from unit A on unit B or C.
Go back to unit A, right click on the rectangle and select "Edit Rectangle Options", this will bring up a properties window, there will be a section called "Sharing" and there will be an option "Common to all units in component", this will be checked, if you un-check this it should allow you to create different graphics for units B and C.
HTH!