How to get rid of #VALUE!

[Larry Alkoff <labradley mindspring com>]

I have a spreadsheet with only 3 calumns,
debits, credits and balance.

Starting from row 1 with a 0 balance,
my formula is
=(b1+c2-d2)

The formula is copied from the first entry and pasted about 150 rows down.

The formula seems simple enough but at row 50 I get repeated entries
of  $VALUE!  all the way down.

The column widths seem adequate.

Can anyone help?

Larry