NUMEROS

Public Function OnlyNumbers(TextBox As TextBox, ByVal KeyAscii As Integer) As Integer
 Dim Char As String
    OnlyNumbers = KeyAscii
    Char = Chr(KeyAscii)
    
    If KeyAscii = vbKeyBack Then Exit Function
    If Char = "." Then KeyAscii = Asc(",")
    Char = Chr(KeyAscii)
    
    If Char = "-" Then
        If InStr(TextBox, "-") <> 0 Or Len(Trim(TextBox)) = 0 Then
            OnlyNumbers = 0
        Else
            If InStr(TextBox, "-") = 0 Then TextBox = "-" & TextBox
            OnlyNumbers = 0
            Exit Function
        End If
    End If
    
    If Char = "," Then
        If InStr(TextBox, ",") <> 0 Or Len(Trim(TextBox)) = 0 Then
            OnlyNumbers = 0
        Else
            OnlyNumbers = Asc(",")
            Exit Function
        End If
    End If
    
    If Not IsNumeric(Char) Then
        OnlyNumbers = 0
    End If
End Function

'Teste
Private Sub Text1_KeyPress(KeyAscii As Integer)
 KeyAscii = OnlyNumbers(Text1, KeyAscii)
End Sub
lyNumbers(Text1, KeyAscii)
End Sub

Permitindo somente números e backspace numa text box via API:

Option Explicit

Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
     
Private Const GWL_STYLE As Long = &HFFFFFFF0
Private Const ES_NUMBER As Long = &H2000
Private defstyle As Long

Private Sub Form_Load()

   defstyle = GetWindowLong(Text1.hwnd, GWL_STYLE)
   SetWindowLong Text1.hwnd, GWL_STYLE, defstyle Or ES_NUMBER

End Sub


Permitindo somente números e backspace numa text box sem API:

Private Sub Text1_KeyPress(KeyAscii As Integer)
   
   Select Case KeyAscii
      Case Is = 8    ' Backspace
      Case 48 To 57  ' Numeros de 0 a 9
      Case Else
         KeyAscii = 0
   End Select
   
End Sub