If the width of a ListBox control is too small to show the content I have found it practical to set the ToolTipText property to reflect on the item the mouse is hovering over.

Code

Private Sub List1_MouseMove(Button As _
Integer, Shift As Integer, X As Single, Y As Single)

Dim YPos As Integer, iOldFontSize As Integer
iOldFontSize = Me.Font.Size
Me.Font.Size = List1.Font.Size
YPos = Y \ Me.TextHeight("Xyz") + List1.TopIndex
Me.Font.Size = iOldFontSize
If YPos < List1.ListCount Then
List1.ToolTipText = List1.List(YPos)
Else
List1.ToolTipText = ""
End If
End Sub

I found this to be more practical than using Windows API to get the horizontal scrollbar.