populating a datagrid

Dear all, I have a table called book with fields bookID,bookName,bookAuthor. And I have a form in which i have a Combo box, a Datagrid and an Add button. The combo box is populated with the bookID. What I want to do is after selecting a bookID from combo box and clicked at Add button the record corresponding to this bookID is displayed on the datagrid. Again after selecting another bookID from the combo box and again clicked on Add button, the details should be populated in the datagrid along with the previous one and so on. I have no idea how to acheived this. Please advice me. Thanking you.