right click on datagrid item

I have created a menu and I'm calling it at right click

on table click s e do if e.Button == e.Button.Right do
(
	popUpMenu rcTest rollout:BitmapLister
)

AND HOW TO MAKE MY RIGHT CLICK IF IT IS NOT ABOVE SELECTION - NOT TO OPEN THIS MENU BUT TO SELECT ITEM INSIDE DATAGRID SIMPLY LIKE LEFT CLICK, AND THEN TO OPEN MY MENU FOR THE NEW SELECTED ITEM

THX IN ADVANCE!!!!