First, there is an additional security check box at the bottom of the script editor - Settings tab - "Open databases in read and write mode". Then it should work.
However, QlikView sends everything found between the "SQL" and the semicolon to the ODBC so it all depends on which syntax it accepts. I have seen both "EXEC" and "EXECUTE"; I have seen cases where you need to put quotes around the SP name.
Finally, you may also need to check that you have rights on the DB to run the stored procedures this way.