Crystal Reports Help in formula to calculate next record

Message

     Hi,
here is a sample data

             ID          Total      Completed   
            -----      -----------    ------------

1
367
    0

2
364
12

3
346
2

4
341
6

5
331
6

6
324
5

7
319
2

8
317
3

9
313
28

10
278
28

11
241
7

I need to create a formula (@actual) that skips the first record then subtract NEXT Record completed from total.
example: 
the first record is 367
second record is 367 - 12 = 355
third record is     355 - 2   = 352
etc... see results below...

             ID         Total         Comp    Acutal
              ---        -----------    -------    ---------

1
367
    0
367

2
364
12
355

3
346
2
353

4
341
6
347

5
331
6
341

6
324
5
336

7
319
2
334

8
317
3
331

9
313
28
303

10
278
28
275

11
241
7
268

I started this formula but it's not working:

local NumberVar x;
x:= {command.Running_Total};
if RecordNumber = 1 then x 
else x := x - next({command.COMPLETED_COUNT})

am I close to the correct formula?

thank you for your help