That would be a nice feature,
but as far as I understand win32 the only option is to launch a new program. Launching another java app to do this would take too long. Maybe one can write a very simple and short cross-platform c/pl/py program to do some IIOP or even a much simpler protocol on localhost with Spark.
Simple protocol could require Spark to open a (configurable*) port, like 127.0.0.1:9999 and listen. With:
“telnet 127.0.0.1 9999”
^C /code one could be able to tell Spark the clicked URL.
(configurable*) … enables me to run two Spark instances and using a clever c program which selects the right Spark client depending on the URL.