Eval Inverse Condition

Hi There,
I'd like to use the eval statement but determine the inverse of the condition. For example, in the statement below, I'd like to set the Visible property based on <%# Eval("![IsConfirmed]")%> ... I realize that the syntax isn't correct but essentially, I want it set if IsConfirmed is NOT true. How do I construct the Eval statement to support that?

<asp:LinkButton runat="server" ID="ConfirmAppointment" Visible='<%# Eval("[IsConfirmed]")%>' />

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