Remote code for a/v input

I have my TiVo bolt connected to a Mitsubishi 73878 DLP television. I have found three of the codes in the group that turn the TV on and off. Those three will also bring up the input menu, but none of them will let me change the input. By pushing the imput button it simply brings all the inputs on screen and then off. On the original remote I have to push the input button and then the left or right arrow to select a different input, but these left and right arrow buttons do not work on the TiVo remote. Does anyone have any suggestions for ways to select imports once the input menu is on screen?