SQL & PL/SQL

Is it possible to stop sqlplus from executing if - say - it's in the middle of a very long plsql script and you've just decided you want to add an extra item or two? Google informs me that ctrl-C is the magic key combination but it doesn't seem to be working for me. I don't have access to enterprise manager, just sqlplus and I'm not logged in with sysadmin level of access - I only need to be able to stop my own script rather than letting it run on and on.

Obviously i realise there could be data integrity issues involved with stopping updates etc but this isn't a problem in this particular case

Thanks