He gets out, you (or your DP) put him back in. You could say, it's bedtime now, back to bed.
He gets out, you (or your DP) put him back in. You could say back to bed.
He gets out, you (or your DP) put him back in. You could say bed now.
He gets out, you (or your DP) put him back in. Say nothing
He gets out, you (or your DP) put him back in. Say nothing.
He gets out, you (or your DP) put him back in. Say nothing.
He gets out, you (or your DP) put him back in. Say nothing.
He gets out, you (or your DP) put him back in. Say nothing.
I could go on, but I won't. You probably will have to 
Good luck - it's worth it in the end.