Assuming you are on windows XP:
Start -> Settings - Control Panel -> Phone and Modem Options
Choose location (default should be enough i think)
click Edit button
in the "To access and outside line for local calls" textbox put the string: 9W8459522,!41
I've never tried it before. but i THINK it should work :)
in fact, maybe put it in both textboxes.
good luck:)