Restrict selection of dorm bed for couple deals

Use Case:

Couple deal promotion for dormitories. Guest should only book just 2 beds for such rate plans, or in intervals or 2 (i.e. 2 beds, 4 beds, 6 beds, etc...)

Suggestion:

Restrict booking for the number of beds to specific intervals for the purpose of promotional pricing. Not just couple deals but also triple/quad/any other number. It's bad UX when we want to promote couple deals, but the site shows 1 bed and 3 beds selection and prompt guest that minimum/maximum booking is 2 beds.