aggregating few values in a datatable

Question

hi,

i am new to programming and C# in general and i have to solve this example.i have a datatable on which i want to perform grouping and aggregation. i have detailed the steps below can someone please guide as to whats the best way to do this:-

the datatable contains, date ,num1,num2,num3(for ex), i need to aggregate this data by date in the following fashion

step 1	sort date by date asc
step2	add up all numbers and assign todays date and enter in array or..
step 3	pick the 2nd date and assign total minus 2nd date value to corresponding measure
step 4	iteratively calulate the numbers for all the remaining dates in the array or.. Using this formula, a[i]value=a[i-1]-a[i]

pls take a look at the input and ouput i expect

INPUT DATA

date	num1
3-Oct-08	100
7-Nov-08	200
20-Aug-09	300
20-Apr-10	400

 

output DATA

date	num1 adjusted
Today	1000
3-Oct-08	900
7-Nov-08	700
20-Aug-09	400
20-Apr-10	0