Use the CanRedo and CanUndo properties to specify whether an undo/redo action is available. Use the AllowUndoRedo property to enable the undo/redo support.

The following VB sample shows how you can implement the Redo command, when user presses the CTRL + J key:

Private Const WM_COMMAND = &H111
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

Private Sub HTML1_KeyDown(KeyCode As Integer, Shift As Integer)
    If (KeyCode = vbKeyJ) And (Shift = 2) Then
        With HTML1
            If .CanRedo Then
                SendMessage .hwnd, WM_COMMAND, &HE12C * 65536, 0
            End If
        End With
    End If
End Sub