>>I've found this https://wpfextendeddatagrid.codeplex.com/ which looks like it might do the trick. I'll try it out this week.
>
>Took a quick look at that link but the 'footer' example doesn't show any sign of being able to do what you want.
>

Was this the footer example? http://wpfextendeddatagrid.codeplex.com/wikipage?title=Row%20Footer

It looks pretty close to what I envisaged, but I'll try it out to see what it can do.