I understand that you are having some issues with your Slingbox, since you are not able to get the right remote control for your set top box.
Since you have not included the information about the specific model for the Motorola set top box, I recommend you to check this link when at the Slingbox location in order to know if this model number included on the supported devices list.
Finding your video source
The video source tool did not find the model Motorola DCT 2224, but I did find a support article regarding the DCT series and how it has caused a lot of problems. http://support.slingbox.com/get/KB-5000291.html
The article reccomends two solutions:
1. Connect the Slingbox using the component outputs.
2. "Make the necessary adjustment: go into the Motorola set-top box's on-screen menu and change the YPbPr output to 480i. (Note: Doing this will affect the way video is output to TVs or other connected devices.)"
I have looked around at the Motorola guides, but I have absolutely no idea how to do the second option. The box isn't connected to a HDTV, so I'm assuming changing to 480i won't be a problem?
If anyone knows how to do this please let me know, I'd love to be able to finally have a remote while viewing my slingbox.