Hi timmo11,
if the complete path of the executable file is „/root/rescan“, than it should work by pasting this into the „Start my own Script“.
You might try to debug, if something is not working as expected: add some logging to the command in the webinterface to see what the command-line output is. In your case you might try this for the „Start my own Script“:
/root/rescan 2>&1 > /tmp/rescan-output
After pushing the button, there should be a file with the output of your script – to open it use „cat /tmp/rescan-output“
