hi,
im trying to do a wireless sync between my yahoo calendar and my blackberry calendar. I have my wifi turned on. In the calendar options it give me an option for wireless syncronization. It is set to 'NO' and will not give me the option to pick 'YES'. Please help. Also is there a way to sync the two while im away from home and not near my wireless network. Like email does. Thanks in advance.

Nope.
You cannot wirelessly sync the yahoo calendar.

why does it give me an option i cannot change?

because the option is present as default.
You cannot change it, because you cannot sync wirelessly.

as a default for what? Appologise if I come across stupid. Im not very technical. Is this option only changeable on other devices? or is it something to do with the software?

here you go, this is an extract from the actual 8900 user manual.

About synchronization
The wireless data synchronization feature is designed to synchronize organizer data (contacts, calendar entries, tasks, and memos) between
your BlackBerry® device and the email application on your computer over the wireless network.

Its present because its an option for certain things.
If your on a BES for example, that option can be changed.
But it doesnt work, if your on BIS, for yahoo, hotmail, etc.

i.e. regardless of whether the option is there, you cant change it, because you cant sync wirelessly to yahoo.

How do you get on BES? Is it a free service?

No. A BES is usually provided by a company, to get work email.