CheckBox multibinding issue - Unable to bind to both

Hello,

I have this line of code:

<CheckBox Content="Show Tool Tips" x:Name="bToolTips" IsChecked="{Binding (local2:ToolTipBehavior.IsToolTipEnabled), ElementName=MWDCommandWindow}" Hint="Show All Tool Tips" />

This binding will enable or disable all the Tooltips throughout the application.  Now what I would like to also do is bind the IsChecked to a boolean value on my ViewModel.  I am having quite a few issues trying to do this through multi-binding.

Could someone show me how to set up a multi-binding (or other way) to do this?

BTW the code to enable and disable all the Tooltips is here:

http://social.msdn.microsoft.com/Forums/vstudio/en-US/98471070-06ee-481e-b586-08b9fb4f15eb/how-do-you-disable-tooltips-in-code-at-runtime?forum=wpf

Thanks!