Convertin checkbox to a boolean value

I am having a problem which is really driving me nuts.

I have a login form with a checkbox on whether or not the user wishes to be remembered the name of the checkbox is autologin: <input type="checkbox" name="AutoLogin">

I am trying to convert the checkbox value to a boolean in the form processing page like this:

Dim autolog
autolog = CBool(request.form("AutoLogin")

Now the thing is when the user does not check the box the script works fine but as soon as the box is check the page returns an error. Am I doing something wrong? Can checkboxes be used in this way?