Karl describes that in WPF 4.0 there is finally an answer to react on a property being altered while being set.
http://karlshifflett.wordpress.com/2009/05/27/wpf-4-0-data-binding-change-great-feature/
Just noticed your post from last year. Sorry it wasn't answered. We received a huge influx of posts last year and we are going through addressing everything that was missed!
The XamDataGrid and all our editors do support this WPF and Wilverlight 4 feature. I have posted a sample application which illustrates this.
Thank you!
Thanks for the sample