Make DataGrid TemplateColumn read-only in code

[Bob]

I have a data grid with a template column. Sometimes I
need this column to be read-only, even in edit mode.
Does anyone know how to do this. I get the other columns
by running through the DataGrid.Columns and testing for
column type. Then I can set ReadOnly for Bound columns or
make the Edit or PushButton columns invisible, but I
can't seem to do this with a template column.
Is there any way to access the control used in
EditItemTemplate for the TemplateColumn in code?

Thanks