Momodot,
     since you have CS2 you can make an action in Image Ready.  Make two resize steps, one for height and one for width. Your third step will be to save optimized as.  After you have recorded these three steps, stop recording.

At the bottom of the action palette click on the insert step button and choose insert conditional. In the pop up menu select image width is greater than  and enter in the width you made the resize width step for. For perform the following action choose include and refer to the step number for resizing the width and click OK.  Repeat this step for the height.  After those two steps are inserted drag them above their respective resize steps.

This will then check the width and if it is bigger than the size you specified it will perform the width resize, then it will check the height and do the same.  Just remember to put the height conditional step right above the height resize step and the same for the width.

All this is in the Photoshop Speed Clinic book that I have.  hope this helps.

P.S.   If anybody knows how to do this in CS3, could you please post it:)

Stew