For anybody who's interested, this is how I solved the field-record relationship issue. Not ideal but does the job!

private void x_InitializeRecord(object sender, Infragistics.Windows.DataPresenter.Events.InitializeRecordEventArgs e) {
            if (e.Record is DataRecord) {
                DataRecord dr = e.Record as DataRecord;
                foreach (Cell c in dr.Cells) {
                    c.Field.Tag = dr;
                }           
            }
        }

Any better solutions, I would love to know.

Thanks Joe.  I think you solved my problem.

In a more general sense, how would one bind a record to a field (field/setting/layout) in XAML.  This I am asking partly as a learning and understanding thing.  I am really stuggling to get my head around XAM, and even more so, Xam Datagrid.  It seems incredibly powerful. I can envisage doing so many things with the datagrid I would never have been able to do.  But I want to get to that point where i feel familair with it and I can understand it's internal structure.  For instance laying out a field and altering it's settings and behaviour based on values within the record itself would seem to be an important and standard feature.  So I'm sure there is a way to easily do this binding, but I have not n smart enough to realise it.

Thanks,

Graeme