CMYK to Spot Color simulation

Is it possible to do the following in Photoshop.

Take a cmyk image - and simulate a spot color replacement for any of the color channels.

In other words, I'd like to see the result/composite of applying a custom color to (say) the Cyan plate, without changing the origonal screen values from the initial CMYK seperations - and see the results in the (non cyan)MYK composite channel.

There SEEMS to be a way to do this in Photoshop - but the answer isn't leaping out at me either in the topics involving color channels or duo-tone (or more) creation.

Thanks for the bandwidth,
monty gabrys

Mode multichannel. Double click on cyan in the channel pallet. In the box that comes up double click on the color swatch on the bottom. Select custom in the color box and then select your PMS color. This is the way I preview when we use other versions of mag.

I don't believe multichannel mode is color-managed so there will be a bit of guesswork, especially when changing the opacity of the spot channel has such a big effect on display even though the numbers do not change.

Multichannel is color managed by the greyscale setting as well as the spot setting.

It's not color managed like a CMYK file where as each C_M_Y_K channel and SPOTS are managed by one greyscale setting in the color settings, settings thingy.

The opacity setting is for a visual reference depending upon how opaque or how transparent the ink set is you want to simulate. Printing directly out of Photoshop? The opacity sitting is invoked so the image will change in transparency relative to this setting. Printing the file to disk? The opacity has no affect.