Script variables do not persist between projects steps. This would lead to lots of difficulties (the least of which is that all global variable names would have to be unique across all steps in a project).
One option would be to modularize the script code into one or more project or global script functions.
Another one would be to store the values from your file into a temporary macro, and then iterate over that for each value:
http://www.kinook.com/Forum/showthread.php?threadid=231