Hittest - Dragging And Dropping Data From A Combobox To A Datagrid

I am dragging and dropping data from a combobox to a datagrid. I'm using VS2010 VB for a windows app. My problem is that the DragDrop event for the datagrid gives x,y mouse positions that are relative to the physical screen that I am using, not the datagrid. So when I use hittest to calculate the row and column the result is out of the bounds of the datagrid. If I manually drag the form around the physical panel, the x,,y coordinates on the dragdrop event chage accordingly. This is really strange.