Locating Under Payments (HELP!)
 

I need to identify all underpayments on a spreadsheet with about 30,000 rows
but I am having trouble coming up with the formula.
I need the formula to apply only to rows with a "Y" in column D (B1-C1) but
column A in the next row(s) is empty I need to subtract B1-(C1+C2+C3).
Sometimes column A is not empty in the row following the "Y" in column D and
sometime one or more rows are empty in column A. I hope someone knows the
answer to this and thank you all in advance for all your help.
A B C D
1 99213 59.2 30 Y
2 -30
3 45
4 36415 4 4
5 90715 70 43.5
6 90632 65 71.93 o
7 90733 80.34 94
8 90713 27.06 27.06
9 90691 40.5 65
10 -20
11 58.41
12 90471 6 7
13 90472 24 20
14 28
15 99395 106.5 10 Y
16 96.5
17 93000 29.7 29.7
18 99213 59.2 10 Y
19 49.2
20 99213 59.2 10 Y
21 49.2
22 99215 131.61 15 Y