Print Transaction Receipt in splitted payement

Hi all :) , often my costumer want payed in a separated mode.. So when i selected one or more items and i click on cash , i would like that software send to printer the transaction. 

So.. I try in action and rule to create an automation rule of this but is fail :( 

For example when a costumer pay one item of 5 total items , with 20 euro , i would that automatically sambapos print a transaction with total and subtotal too ;) Can  you help me!? 

Thanks :)