Merging multiple lines if one range selcted

Hi All, so I have a weird question. 

I have created a small hotel template for reservations 

I have as you can see below created dates and a range of selections

I was wondering how or what formula (if any) i can use to 

when I enter the number of nights the

guest name

booking source

villa size

cost per night and

total cost cells all merge automatically so i don't have to merge them each time one by one

then what formula do i put in to auto add the cost per night to the number of nights'

sorry if this is confusing but it will help me so so very much 

thanks

Steve