A very precise way to remove a colour cast

I've just stumbled into a way to remove a colour cast with great precision and subtlety.  It accomplishes the same thing as the Colour Variations, but with much greater control.  Don't know if it's common knowlege or has been mentioned before, but here it is:

1. Copy your image to the Clipboard.
2. Create a Hue/Saturation adjustment layer, which will automatically have a full image white mask.
3. Alt+click on the H/S mask to load it into the Editing window.
4. Paste your copied image into the mask.
5. Use the H/S settings to colorize the image, using a colour that's complementary to the colour cast you want to remove.  In this case, I wanted to lessen the red, so I used a cyan colour:
   
6. Set the blend mode of the H/S layer to "Screen".

The layers look like this:

The before and after:

When you look at all the settings at your disposal (Hue, Saturation, Lightness, Opacity), you're bound to find precisely the result you're looking for.

Ken