Hi,
You will need to set the Grid's EnableKeyboardNavigation to true. For drop down list box, you will need to handle your CustomColumn's ClientSideBeginEdit to focus your list box with a timer:
Code: JavaScript
function your_client_side_begin_edit_handler()
{
setTimeout(function()
{
document.getElementById("your_drop_down_id").focus();
}, 100);
}
Once you give focus to your listbox, you will be able to use keyboard to select item.
Thanks!