rotate two object the same time

How can I let two mesh-objects rotating on there own pivot point at the same time without selecting them both.
So if I rotate a box on the left the box on the right must rotate also.

Not sure if this will help:-

Select the default cube, ALT+D. Set pivot to individual centres. Tab into Edit mode and hit R.
It will work with S and G also.

I mean using constraint or parenting for animation with the IPO curve editor

You could copy the first object’s IPO curve to the Buffer, then copy from the Buffer for the second object.
If you make any changes to the first object’s curve, it won’t automatically update the second object’s curve - so there is probably a more elegant solution.

EDIT - What about the ‘Copy Rotation’ constraint?

Ok it works now with copy rotation constraint.
Selected the wrong target first so I thought it did not work… How silly