On a right mouse click, the DropHighlight property is set to the node that was clicked upon but only within the MouseUp event. It does not matter if FullRowSelect is true or false.

Code:
Private Sub TreeView1_MouseUp(Button As Integer, Shift As Integer, x As Single, y As Single)
    If Button = vbRightButton Then
        If Not TreeView1.DropHighlight Is Nothing Then
            TreeView1.DropHighlight.Selected = True
        End If
    End If
End Sub
If you need to find the clicked upon node in the MouseDown event use this code

Code:
Private Sub TreeView1_MouseDown(Button As Integer, Shift As Integer, x As Single, y As Single)
    Dim lngIdx As Long
    Dim oNode As Node

    If Button = vbRightButton Then

        Set oNode = TreeView1.HitTest(x, y)

        If oNode Is Nothing Then
            'click did not occur directly on a node's text
            'check if it may have occurred elsewhere along the node's row
            For lngIdx = 1 To TreeView1.Width Step 100
                Set oNode = TreeView1.HitTest(lngIdx, y)
                If Not oNode Is Nothing Then
                    oNode.Selected = True
                    Exit For
                End If
            Next
        Else
            oNode.Selected = True
        End If
    End If
End Sub