Hi Shawn,
This is probably not the best place to ask such question as by first impression it's not Visual WebGui related directly, except maybe for the fact that you will open that link from within a Visual WebGui application.
I also must admit, that I would have said this url was not valid, as you are using both "http://" and "webcal://" as a part of the same Url. According to Wikipedia article here, this is not a valid option.
If you insist this link is indeed valid, I would suggest that you try seeking information in a more outlook oriented forums where this type of link would be discussed.
Palli