How can I tell if the banding is in the image or if it's just the display?
In PS, on the Info palette at the right hand side there is an eyedropper; right click on it and change the display to HSB.
Now, move the cross hair over the banding part and watch B(rightness): if it changes, while you move the cursor and the display does not change, then buy a better monitor (though it might be the brightness/contrast adjustment).
However, if B does not change continuerly but several units at once, then the banding is in the image. Post one of the raw files indicating the location of banding, and the adjustment parameters, and let's take a look of that.