Retrieving the Item in a Listbox the mouse is currently over.

Private Sub Form_Load()
  Dim i As Integer
  ' populate the listbox with the
  ' indexes for each entry

  For i = 0 To 50
    
    List1.AddItem i, i
    
  Next i
  
End Sub

Private Sub List1_MouseMove(Button As Integer, Shift As Integer, x As Single, y As Single)
 Dim iSelected As Integer
  
  ' retrieve the index the mouse
  ' pointer is over (-1 represents
  ' mouse is over nothing)
  iSelected = GetListItemFromPt(List1, x, y)
  
  ' select the item the mouse
  ' is currently over
  If Not iSelected = -1 Then
    
    List1.ListIndex = iSelected
  
  End If
End Sub

Public Function GetListItemFromPt(plist As ListBox, x As Single, y As Single) As Integer
  Dim bFound As Boolean
  Dim rCur As RECT
  Dim iIndex As Integer
  Dim iPixX As Integer, iPixY As Integer
  
  ' convert the coordinates to
  ' pixels (remove the next two
  ' lines if you will be passing
  ' the coordinates in pixels)
  iPixX = Me.ScaleX(x, vbTwips, vbPixels)
  iPixY = Me.ScaleY(y, vbTwips, vbPixels)
  

  For iIndex = 0 To plist.ListCount - 1
    
    ' get the coordinates for each
    ' item in the listbox in its current
    ' state, if Top is less than 0 or Bottom
    '
    ' is greater than the height of the
    ' listbox then the item is currently off
    '   screen
    SendMessage plist.hwnd, LB_GETITEMRECT, iIndex, rCur
    
    ' if passed corrdinates are within
    ' the bounds of the current item than
    ' exit the loop and return the index

    If iPixY >= rCur.Top And iPixY <= rCur.Bottom Then
      bFound = True
      Exit For
    End If
  Next iIndex
  
  
  If bFound Then
  
    GetListItemFromPt = iIndex
    
  Else
    
    GetListItemFromPt = -1
    
  End If
End Function