A little more information about how things are laid out on your worksheet
would help us help you.
A possible start? Your original amount is in A1, the values to be
subtracted from that original amount are in column B. Then a formula like
=A1-SUM(B:B)
in cell A2 (or any cell not in column B) would show the current balance.
A second possibility:
Original value in A2
First payment in B2
for initial balance, in C2 you could put = A2-B2
At this point you continue putting 'payments' in column B, and in C3 you put
this formula:
=C2-B3
and that will fill on down the sheet keeping a running balance for you.