Photoshop question - how to switch blending mode using scroll key

[novetan]

In photoshop CS3 using Windows under blending , we can simply use the scroll key (arrow up or down key) to scroll from normal>dissolved>darken>mulitply and so forth to see the various effect.

But in Mac, it didn't behave the same. Pressing the scroll key has no effect. I have to individual point the cursor at various blending mode for it to take effect.

Have I miss pressing some additional keys to scroll like what I can do in Windows?

Thanks