calculate only the Total row in straight table

[Xabinav]

Hi, I want to calculate only the Total row for Price For KM by the following way - 
Last (KM) / Last(Cumulative Amount)  -  

The formula for 'Price For KM' is  (KM/ Cumulative Amount)

Sample Date:   

* In the original I present in a straight table

Order ID	Cumulative Amount	KM	Price For KM
10	200	1000	5
11	250	1400	5.6
12	280	1800	6.42
13	350	2500	7.14
			7.14

What is the way to do it? I tried several ways, I get NULL in Total line 

Thanks 

[vincent_ardiet_]

Try something like : Bottom("Price For KM") or Bottom("KM"/"Cumulative Amount") both should work.