The ListView control exposes the AfterLabelEdit event to let the programmer validate the text entered in a ListItem, but there is no way to trap keys as they are typed by the user. This prevents you from discarding unwanted characters while the user types them.

You can work around this problem by subclassing the Edit control that the ListView control creates when entering the node edit mode. The following code uses the MSGHOOK.DLL library, that you can download from the FileBank on this site, to discard digits and convert all text to uppercase:

' REQUIRES THE MSGHOOK.DLL LIBRARYPrivate Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal _    hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _    lParam As Any) As LongConst LVM_FIRST = &H1000Const LVM_GETEDITCONTROL = (LVM_FIRST + 24)Dim WithEvents TVHook As MsgHook' start subclassing of the Edit control used when in edit modePrivate Sub ListView1_BeforeLabelEdit(Cancel As Integer)    Dim editHWnd As Long        ' get the handle of the TreeView's Edit control    editHWnd = SendMessage(ListView1.hWnd, LVM_GETEDITCONTROL, 0, ByVal 0&)    ' subclass it    LVHook.StartSubclass editHWndEnd Sub' stop subclassing when exiting edit modePrivate Sub ListView1_AfterLabelEdit(Cancel As Integer, NewString As String)    LVHook.StopSubclassEnd SubPrivate Sub Form_Load()    Set LVHook = New MsgHookEnd Sub' discard digits as they are entered by the user' and convert all text to uppercasePrivate Sub LVHook_BeforeMessage(uMsg As Long, wParam As Long, lParam As Long, _    retValue As Long, Cancel As Boolean)    If uMsg = WM_CHAR Then        ' wParam contains the character code        If wParam >= 48 And wParam <= 57 Then            ' discard digits            Cancel = True        ElseIf wParam >= Asc("a") And wParam <= Asc("z") Then            ' convert to uppercase            wParam = wParam - 32        End If    End IfEnd Sub