far as I know for a tray button you use /macro, but hell if I know 
Just use /macro to create your button. Pressing the number keys will activate whatever is in that slot (on the lower tray), be it a power, emote, or some chat text.
Alternately, use /bind, and you won't need an actual button at all.
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/macro Text "do some stuff$$some other stuff"
This will create a button on the power tray with the label "Text". It's "higher performance" than keybinding: keybinds are local, when you hit the key it has to sennd all the commands to the server, macros are server-based, only the keystroke needs to be sent to the server.
I use macros when I want to combine a power with a message, to avoid any delay in the power executing. Stateman suggested making macros, then binding keys to the macro activation for performance, instead of making long keybinds.
One problem with this is you can't store or edit macros or move them between characters easily, as you can with keybinds.
Another problem is that you can't "cycle" macros. With keybinds, you can actually cange your keybind as part of the keybind, so you say something different each time. With macros there's basically no way to do this.
/macro <macroname> "command $$ next command"
besides that refer to keybind referances... they list all the availible commands and little tricks you can do...
using the origional posters example
"local I crush your head!$$powexec_name Crush"
would be correctly macroed as
/macro crush "local I crush your head!$$powexec_name Crush"
this would create a new "bubble" in your quickbar that could be clicked (or acrtivated with the numbers as any other "bubble"...
good luck
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I'd like to create a powertray button bind, but I'm not sure how. For exmaple:
"local I crush your head!$$powexec_name Crush"
Now, I could bind that to the "1" key, but if I want move the Crush power to location 2 I have to rebind it, which can get inconvenient.
Ideally, I'd like to create a button in my powertray that does the above command combo that I can move around the powertray.
Any help?