I think the easiest way to do this is with the selection tool in the Enfocus Inspector grab a portion of the screen and manually change it to the desired PMS screen and then add the Tinted colour to the user swatches. (you can do that in the drop down menu of the Enfocus Inspector with the object selected). Then in the global change grab the tint you want to change and then as your target select the PMS tint you are wanting from the user swatch that you just created.
Hope this makes sense.