A more intuitive way to dynamically alter an expression for jit.expr. Uses the standard max message variable format (1,2, ...) for choosing elements from a list (including symbols). The ob ject must first be initialized with an expression specified with the ’expr’ message following the exact same conventions of the jit.expr 'expr' message meaning that expressions for specific planes are seperated by quotes as demonstrated in this patch. Also, the ', ' character must be escaped ('\,') as with all max messages. When floats, ints, or lists are sent to xray.dynamicexpr.js, a list of symbols is output with the appropriate substitutions made.