Thanks to Lada Simicek for this (and many other) tips.

This tip shows you how you can select an item in the listbox using right mouse button. This is useful when you want to show popup menu, for example. This tip doesn't uses any API functions. All the code does is calculates the index of the item which you has clicked on from mouse's co-ordinates. For this code to work, it needs to know whether the listbox's property Style is set on Standard or CheckBox. Furthermore it is necessary to set the form's property FontSize on the same as ListBox (this is caused because the property TextHeight is only used in Form control.

Here is the short example that shows you how you can correctly select an item in the listbox via right mouse button:

Please, insert on the Form1 one listbox named List1. Try changing its style properties too. (Please note that this code does not appear to work on some systems. If anyone works out why, please email me!)

Private Const STANDARD_LISTBOX = 1
Private Const CHECKBOX_LISTBOX = 1.05

Private Sub Form_Load()
Dim i As Integer
    For i = 1 To 250
        List1.AddItem "Item No." & i
    Next i
End Sub

Private Sub List1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
 Dim intIndex As Integer
 Dim dblStyle As Double
   
    Select Case List1.Style
    Case 0 'Standart
        dblStyle = STANDART_LISTBOX
    Case 1 'CheckBox
        dblStyle = CHECKBOX_LISTBOX
    End Select
   
    If Button = vbRightButton Then
        With List1
            Picture1.FontSize = List1.FontSize
            intIndex = ((Y / Screen.TwipsPerPixelY) _
            ((dblStyle * (Picture1.TextHeight("A"))) _
            / Screen.TwipsPerPixelY)) + .TopIndex
            If intIndex > .ListCount - 1 Then intIndex = -1
            .ListIndex = intIndex
            .SetFocus
        End With
    End If
End Sub