only an idea:
create a file where you save your sequence of characters.
than a small shell script
paste <path to sequence file>
you have to do the file executable. use the right click menu > Properties > second tab > the little checkbox
naow i would try to insert the path to the shell script into the lxde-rc.xml file.
<action name="A Burst">/home/<user name>/scripts/<file name>.sh</action>
again it is an idea only
i don't know whether it works. i couldn't test it.