Applying adjustment layer to a group of layers

Is there a method to apply an adjustment layer to a group of layers?

I have a curtain on one layer of a Photoshop CS4 document.

I duplicated the curtain twice and repositioned the copies.

Now I'd like to use an adjustment layer to change the color of my curtains without affecting the rest of the composition (and I can't move the curtains down to the bottom because they need to sit above other elements).

I tried grouping my 3 curtain layers together and then applygin an Adjustment Layer>hue>colorize - but that's affecting the whole composition.

And when the layers are grouped, holding ALT while hovering between the adjustment layer and the group does not bring up the special icon that lets you apply the adjustment just to the layer beneath it.

Would apprecaiate andive on how to apply an adjustment layer to a group of layers.

(I can go back and apply my adjustment to the original curtain then reduplicate and reposition, but would have to repeat that procedure every time change color preference).

Thanks?