I don't know of a way to cycle through the inputs, unless you buy a cable. However, you can program buttons individually so that the various inputs are selected. I doubt you have so very many.
Here are some 5 digit EFCs to assign to buttons. First you should just test the EFCs. That's easy to do. Make sure the remote is in AUX mode, then tap (don't hold) Setup, followed quickly by entering the 5 digit EFC. For example to switch to BD, tap Setup and enter 01897. When you enter the last digit (7), the remote should send the IR signal to the Denon, and it should switch to BD input.
Assuming the tests work OK, pick buttons for each needed input. I'd probably use the A, B, and C buttons, if I were only using 3 inputs, or include the Page up and Down buttons to make a nice row of 5 buttons that each select an input.
To assign the EFCs to the buttons, be in AUX mode, and
1) Press Setup until 2 blinks
2) Enter 994 (2 blinks)
3) Tap Setup
4) Enter the 5 digit EFC (e.g. 01833 for SAT/CBL)
5) Tap the button to assign to (e.g. A)
The remote should blink twice to indicate it understood the assignment.
See the link to the Wiki in mdavej's signature to see more extensive instructions on manually programming the remote.