Inserisci in un modulo questa function:

Public Declare Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" (ByVal hwnd As Long, ByVal lpOperation As String, ByVal lpFile As String, ByVal lpParameters As String, ByVal lpDirectory As String, ByVal nShowCmd As Long) As Long


e poi metti questo codice in un pulsante:

ShellExecute Me.hwnd, "open", "miapagina.htm", "", "", SW_SHOW

ciao!