OK, I decided to try it out.  I only had a few minutes so I did it using the SqlDataSource.  Binding a RadGrid to a SqlDataSource in DNN is typically codeless and does not use the DataProvider or Controller.  You just create your stored procedures and tell the grid which one(s) to use.  Your requirement was to add moduleid to the sql table when a new row is inserted.  You will notice moduleid is nowhere in the grid itself.  It is used when originally binding the grid so only rows added for this module instance show in this grid.  The moduleid is passed to the SqlDataSource Insert command looking at a label control within the module which has its text property set to the current moduleid.  If you download the source and look at the codebehind, you will notice there is only one line of code.  That line sets the label text to the moduleid.  Everything else in this module is handled using the RadGrid Automatic Insert/Update/Delete and the SqlDataSource.

If I have time later I'll do it again using an ObjectDataSource which uses the DNN Controller.  I will say, though, I use the RadGrid a lot and I don't believe I've ever used an ObjectDataSource in production.  When a SqlDataSource just won't do it (which is rarely), I find good ole fashion codebehind binding using the "old dnn way" of Info/DataProvider/Controller/SqlDataProvider works best.  This does, of course, presume your database is SQL Server.  LMK how you make out.

http://www.tiurl.com/CodeSamples/RadGridBDay.aspx