How to stop people using toilet when emptying it

oraclebhoy

had on THREE occasions now the female members of my family having a no1 while I was away emptying the cassette.

i have tried telling them I'm emptying it, I have even tried a flashing red light in the place of the cassette (very affective, looks like the bowl is on fire) but they don't have time to look before they go.

anyone came up with a fail safe solution that doesn't involve locking them out if the caravan?