The input selects and the rest of the commands should be in the database so you shouldn't have to enter this stuff. In the odd event that you have equipment that has never been seen by any Harmony remote then you have to learn to teach commands (with with Learn or Raw, which you can learn about - I had to do this for my TV - it was a Harmony virgin - a rare bird). With each activity you are completely in it or completely out of it. You can't interrupt with commands from other sources. Think through the logic - draw diagrams of what you want to do and how if you didn't have the Harmony. And then have it do exactly what you do. You can create as many activities as are necessary to achieve the result.