Don the technicalities of the High Pass filter are beyond me. so I've just been doing a search of the web and found this.
http://www.earthboundlight.com/photo...photoshop.html
Hope this will help you understand the High Pass method of sharpening a little better.
My workflow is just a little different, have tried this method out, which is very similar to the way I do it, but must admit the workflow is better than my method.
I will play around some more before deciding whether to change, but it's looking if my workflow will be changing.
I'm very pleased you asked the question, so will probably do a little more searching.
Harry
ps. have just spent the last hour at the earthboundlight site, no doubt this will become a firm favourite of mine.
Well worth a visit