Nice,
Unless I 'm really missing what you're trying to do, you just need to specify those channels in your current list. For example: to add AI15, AI20 and AI25 to your scan you would use this list...
AI0:AI1, AI15, AI20, AI25, AI45:AI49, AI56
Hope you find it helpful. If you need more info, let me know.
Scott Menjoulet