Nu2Java,

Create a private function in the userform code module:
Private Function DisableButtons(ByVal strEnable As String)
    
    Dim ctrl As Control
    
    For Each ctrl In Me.Controls
        If TypeName(ctrl) = "CommandButton" And ctrl.Name <> strEnable Then
            ctrl.Enabled = False
        End If
    Next ctrl
    
End Function

Then put this code in each of the command button click events:
Private Sub CommandButton1_Click()
    
    DisableButtons Me.ActiveControl.Name
    
End Sub

Private Sub CommandButton2_Click()
    
    DisableButtons Me.ActiveControl.Name
    
End Sub

Private Sub CommandButton3_Click()
    
    DisableButtons Me.ActiveControl.Name
    
End Sub