I would use Pick Directory()
Names Default To Here( 1 );
Pick File(
"Select JMP File",
"$DOCUMENTS",
{"JMP Files|jmp;jsl;jrn", "All Files|*"},
1,
0,
"newJmpFile.jmp"
);
and then the Files in Directory()
Files In Directory( "$HOME" );
to get started with what you want to do.
Look to the Scripting Index for the examples and definitions
Help==>Scripting Index
Jim