Option Explicit
Private mbCapturado As Boolean
Private Sub Command1_Click()
   If Not mbCapturado Then 
        gHW = Text1.hWnd
        Activa
        mbCapturado = True
   Else
        mbCapturado = False
        Desactiva
        gHW = 0
   End If
End Sub

Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
    If mbCapturado Then Desactiva
End Sub

Option Explicit

Public Declare Function SetWindowLong Lib "user32" Alias _
"SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, _
ByVal dwNewLong As Long) As Long

Public Declare Function CallWindowProc Lib "user32" _
Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, _
ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, _
ByVal lParam As Long) As Long

Public Const GWL_WNDPROC = (-4)

Public Const WM_CONTEXTMENU = &H7B

Global lpPrevWndProc As Long
Global gHW As Long

Public Sub Activa()
    lpPrevWndProc = SetWindowLong(gHW, GWL_WNDPROC, _
    AddressOf gWindowProc)
End Sub

Public Sub Desactiva()
  Dim temp As Long
    temp = SetWindowLong(gHW, GWL_WNDPROC, lpPrevWndProc)
End Sub

Public Function gWindowProc(ByVal hWnd As Long, ByVal Msg As Long, _
ByVal wParam As Long, ByVal lParam As Long) As Long
    If Msg = WM_CONTEXTMENU Then
        Debug.Print "Interceptado  WM_CONTEXTMENU ( " & Now & ")"
        gWindowProc = True
    Else ' Send all other messages to the default message handler
        gWindowProc = CallWindowProc(lpPrevWndProc, hWnd, Msg, wParam, _
                    lParam)
    End If
End Function

Private letra As String

Private Sub Text1_KeyDown(KeyCode As Integer, Shift As Integer)
  letra = ""
  If KeyCode = 46 Then
    letra = "p"
    KeyCode = 0 'así no tiene que borrar el carácter
  End If
End Sub

Private Sub Text1_KeyUp(KeyCode As Integer, Shift As Integer)
  If Len(letra) > 0 Then
    Text1.Text = Left(Text1, Text1.SelStart) _
                 + "p" _
                 + Right(Text1.Text, Len(Text1) - Text1.SelStart - 1)
  End If
End Sub

If KeyCode = vbKeyDelete Then 
KeyCode = 0 ' Anular el delete
SendKeys "{p}" ' Simular el tecleo de la p 
End if 

Private Sub Text1_KeyDown(KeyCode As Integer, _
                            Shift As Integer)
    If KeyCode = 46 Then
       KeyCode = 80
    End If
    
End Sub