Generally is disclaimer showed for any new connection.
If you want to have a guest network with more frequent disclaimer provision, and do not want to display disclaimer too often for regular employees .. (if I got that correctly) .. then how about to split those two networks ?
Keep one set of settings, network/SSID, for users/employees only.
And second, with different setup, for true guests.
Tom xSilver, planet Earth, over and out!