How to get cumulative decreasing values by substracting from the previous row.... in a dynamic added

[Former Community Member]

I have pdf table like this:-

Header 1	Header 2	Header 3	Header 4	Header 5	Header 6	Header 7
From	To	No. of Days	Balance	Date
1	2	<ADD Button> / <Del Button>	3	4	5
This	Row	is	730	to	be	hidden
DateFieldFrom	DateFieldTo	DateFieldTo-DateFieldFrom(Some No1.)	Remaining1=uppervalue(730)-Some No1.

Now when i click the <add  rows button>  rows are to be added and i have to get the valuesof Remaining2(Remaining1- Some No.2 )in the Added Balance Row

how will i do this?