I feel like this should be pretty simple to do, but I can't get it to work. I have a tabbed group on my reporting surface, and I want certain tabs to be visible to only people in certain roles. So, in Edit mode, I go to the Tab group in the ribbon:

When I click on Visibility, I get a list of the tab names where I can enter hidden, enabled, or disabled. Or I can use an If statement that evaluates to one of these values. For example, I enter:
<%=If(CurrentUser:Users.Role="Admin","enabled","hidden")%>
I expect this to make the tab visible to only Admins, but it doesn't. Probably something in my syntax.