Trying to wrest a "production" quality experience from MC21 is challenging, and time-consuming.
I know how you feel. I find MC's remote setup a little confusing, and combined with Logitech's, it can be time consuming.
Here is how you can do it with a Logitech remote and using a Media Center Core command.1. Set up a new soft button for your Harmony remote on the Logitech site. Position it where you want it in the menu structure, and assign a free key combination to it. I assigned Alt+2.
Note 12. Save that and update your Harmony remote.
3. Go to MC Options/Remote Control/Commands.
4. Click Add, Select Custom, give your new command a name. I'm using "Previous TV Channel".
5. Click Add Run, enter the Executable Filename = "MCxx.exe" where xx = the version you are running, no quotes. For me, MC21.exe.
6. Enter the Parameters, which is "/mcc 10064", no quotes. This is the
Media Center Core Command for switching to the last played TV channel.
7. Click OK to close the "Edit Remote Command " dialogue.
8a. Highlight your new "Previous TV Channel" command. Click "Start Learning", then press the new soft button on your remote so that MC learns the IR command associated with it.
Note: This is where MC warned me that it can already handle, and already uses, ALt+2. I used it anyway, for now.
8b. Click "Learn" to dismiss the warning message, then click "Stop Learning", then OK.
Done.
Now start watching TV. Switch to a second channel. Then press your new soft button, and MC will switch back to the first channel. Press it again and MC will switch back to the second channel. Etc.
Note 1:I used Alt+2 for this button, but as MC already uses Alt-2 it warned me that it could already handle that command. I will have to find another free key combination to use, if I wish to keep using the standard
MC Keyboard Hot-Keys. In fact, I should be able to have the Harmony learn a new button from one of my old remotes that includes a switch to previous channel, use that in my soft button definition, and then have MC learn this IR command for use with this function. There should be no conflict with MC Keyboard_Hot-keys then.
I have a Logitech Harmony 880 remote, and use the "Windows Media Center SE" device profile, rather than the original "MCE Remote" device profile. Frustratingly that profile doesn't include a "Ctrl+B" command. It includes eleven "Ctrl+key" commands, but not "Ctrl+B". Annoying actually. I suspect that if the Harmony could send a Ctrl+B directly that MC would receive that and it wouldn't need to learn the IR command.
Worse, I can't add Logitech's "Media Center PC" "Microsoft" "MCE Keyboard" device to my Harmony 880 remote to see what you are doing. I can't add any "Media Center PC" devices at the moment actually. Either something is wrong with the site, or Logitech's software thinks I have all "Media Center PC" devices already, so I can't add any more. If I could add that device to my Harmony I would have a much larger selection of key combinations I could use.
I don't think your "SkipBackward" function is sending a Ctrl+B. In fact, you shouldn't be using one of the predefined standard MCE functions. You need to use some key combination that hasn't already been assign to a function.
Are you unable to enter the Ctrl+B key combination for a new soft button on the Harmony One? That would be what I tried first if I was able to use the "MCE Keyboard" device.