Dialog box

How can I create a dialog box that prompts me for four dates (Date1, Date2, Date3, and Date4) and validates them to ensure the user doesn't enter incorrect dates? Once the user enters the correct dates, I'll call an external import script. The idea is to automate this process. Any ideas on how to build this dialog box would be greatly appreciated. Thanks.

Option Explicit

Sub main

Call menu()

End Sub

Function menu()
Dim dlg As Ndialogo
Dim button As Integer
button = Dialog(dlg)
End Function
This is as far as I can get; I don't know how to validate the four dates captured in the TextBox of each one.