ASP: Validating User Input to Avoid Attacks

  If ValidateInput(MyUrl) Then   
    Response.Redirect (myURL) 
  Else 
    Response.Write("URL was invalid.") 
  End If 

  Function ValidateInput(sInput) 
    Dim reValid 
    Set reValid = New RegExp 

    reValid.Pattern = "^[\w\.:\?&=/]*$" 
    reValid.MultiLine = False 
    reValid.Global = True 

    ValidateInput = reValid.Test(sInput) 
  End Function 

(http://msdn.microsoft.com/en-us/library/ms525361%28v=vs.90%29.aspx)