I bound radgrid programatically with using GridTableView but i don't
have any idea how can i get value of detailtableview bound column value
on itemdatabound any budy have idea?
A better question is when are you trying to get access to the value? The item databound event will give you access to the object which is bound to the row. You could then case the e.Item to the proper data type and have direct access to the item you are looking for.
If you are trying to find the value after an edit then things get complicated. You could add the column to the "DataKeyNames" list so that the values are preserved. You can then extract the value from that collection.
The online help files do have several examples on how to do this of course.