[Leica] Advice sought on colour-correcting magenta cast black fabrics in Photoshop

[geordiepete211 at yahoo.co.uk (Peter Cheyne)]

I would like to make some prints taken from M8 photos.  A few of these  
photos have the magenta cast on black fabrics photographed in tungsten  
light.  I have used
the selective brush in Lightroom to darken the fabric in photo, but  
the tool cannot be used in other photos where it's application proved  
too fiddly.  I have heard that
it is easier to turn this magenta-purple into black in Photoshop (I  
use Photoshop 7, but haven't used it for a while).

Could anyone please share with me a simple workflow to colour-correct  
M8 photos in Photoshop?

Here is a sample photo typical of what I wish to correct.  My t-shirt  
is actually close to that colour, though a little bluer and darker.   
Her top should be almost black.
I don't mind my t-shirt turning blacker in the process.

http://www.facebook.com/photo.php?pid=4901228&id=671857576

Peter Cheyne