Passing values from master table to details table in Insert

I have a radgrid that has two levels of hierarchy.  The very top or first level of hierarchy there is one column that displays information.   Each row of that column expands to another table or level of hierarchy with more specific information.  On the 2nd level of hierarchy the user can edit, insert, or delete records from the expanded table.  Upon clicking "add new record" I want to pull the column text value from the very first level of hierarchy and carry it over as an default value into the insert mode of the 2nd table.  How would I go about doing this.