I understand that you want to know how to "restrict" the access to one of your Slingbox Classic units.
In this case, your best option is to create a Sling Account for guest users. The following article will provide you with the steps to follow:
I recommend you to check this article and give it a try.
Hope this helps!
Thanks for the reply and at 1st it makes sence, but I cannot find the page you mention - anywhere If i go to my slingbox profiles on here I cannot see anypage that looks like the on in the link, I have even looked for it localy by running the setup wizzard of the slingbox on my PC ???????
where am I going wrong, this is really doing my head in