How to export additional calendars

[supersadie]

Hi
I use Outlook and apart from the 'standard' calendar (cunningly called 'calendar') I have two more calendars under 'other calendar' and 'shared calendar'. I didn't choose to put them there; that's just where they decided to locate themselves.
I want to save them all to a single iCal file, although I don't mind if I can just save them all as separate files, but there seems to be no way I can find to do this. I've tried ticking all the calendar boxes before saving, but only the standard Calendar file is exported. If I untick that box and tick the other calendars, there's no option to save the calendar at all.
Can anyone help?
Many thanks.
Sarah