Split cell value (numeric) and input half of the number into 2 cells.

I have a calc sheet that I wrote for plan pricing along with unit pricing. Sometimes we do 2 for 1 specials. As is now, we have to calculate the pricing and punch it into 2 cells manually. Is there a way for Calc to look at a number in a cell and then have a drop down or button I can click that will look at the number, split it in half and then update 2 cells with that number? Example - Cell A3 has number $30. Can I do a drop down box and have it split A3 into $15 and B3 $15 by itself? Thanks