Since 10463 is the setup code, I'm guessing the image of the remote is close but not exactly your remote-- I suppose that your remote has a red OK/Select button instead of grey.
Anyway, the following condtions need to be met.
1) The Dynex must be capable of responding to an IR signal which commands the functions you are interested in, or respond to a sequence of commands that will do the function. For example, it should respond to an IR signal which tells it to change to HDMI1 or perhaps to the sequence .
2) You'll need to know or find out the corresponding function codes.
3) The functions codes (EFCs) will need to be assigned to the PIP buttons.
Do you switch inputs with a single button press on the original remote, or with a series of button presses?
For the moment, I'll assume that a single press works, or the TV can respond to a single press ( a discrete IR signal) even if the original remote doesn't have such a dedicated button.
You can use the Lookup Tool
to see the normally used EFCs with setup code 10463, and try plausible functions. Select Device Search, and TV 0463 (not 10463) as the setup code. Click Search, and then click the resulting EFC link. There you'll see, e.g., that Sleep is listed as EFC=123.
Try this code on the Comcast remote by first pressing TV, then press Setup [edited to fix error] briefly. Then quickly enter 00123. When you press 3, the TV should go into sleep mode (if that is how the sleep function is reached with the Dynex).
For the input functions, well, try the likely candiddates, like "Input 5". If you don't find the function you want, you can try an exhaustive search of all 256 EFC possibilities between 00000 and 00255. Takes about 30 minutes, but be sure to watch for a reaction from the Dynex after trying each EFC. You wouldn't want to have reached a service menu, and not notice that fact.
Once you have the EFCs that you need, assign them semi-permanently by using the 994 EFC keymove command. See instructions here
If it turns out that you need a sequence, post back and we'll go through the 995 command to setup macros.