formula to incrementally subtract a value form cells in column from bottom up

[jetpack]

have sheets with 100k+ rows of data. values in some cells are calculated values. I need to incrementally subtract a value from an entire column, bottom up.

example data

[TABLE="width: 298"]
<colgroup><col><col span="2"><col><col></colgroup><tbody>[TR]
[TD][/TD]
[TD]A[/TD]
[TD]B[/TD]
[TD]C[/TD]
[TD]D[/TD]
[/TR]
[TR]
[TD="align: right"]1[/TD]
[TD="align: right"]370[/TD]
[TD="align: right"]19242[/TD]
[TD="align: right"]19192[/TD]
[TD="align: right"]18542[/TD]
[/TR]
[TR]
[TD="align: right"]2[/TD]
[TD="align: right"]461[/TD]
[TD="align: right"]18872[/TD]
[TD="align: right"]18822[/TD]
[TD="align: right"]18222[/TD]
[/TR]
[TR]
[TD="align: right"]3[/TD]
[TD="align: right"]258[/TD]
[TD="align: right"]18411[/TD]
[TD="align: right"]18361[/TD]
[TD="align: right"]17811[/TD]
[/TR]
[TR]
[TD="align: right"]4[/TD]
[TD="align: right"]-960[/TD]
[TD="align: right"]18153[/TD]
[TD="align: right"]18103[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]5[/TD]
[TD="align: right"]-58[/TD]
[TD="align: right"]19113[/TD]
[TD="align: right"]19063[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]6[/TD]
[TD="align: right"]-120[/TD]
[TD="align: right"]19171[/TD]
[TD="align: right"]19121[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]7[/TD]
[TD="align: right"]-72[/TD]
[TD="align: right"]19291[/TD]
[TD="align: right"]19241[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]8[/TD]
[TD="align: right"]-39[/TD]
[TD="align: right"]19363[/TD]
[TD="align: right"]19313[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]9[/TD]
[TD="align: right"]5[/TD]
[TD="align: right"]19402[/TD]
[TD="align: right"]19352[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]10[/TD]
[TD="align: right"]407[/TD]
[TD="align: right"]19397[/TD]
[TD="align: right"]19347[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]11[/TD]
[TD="align: right"]-726[/TD]
[TD="align: right"]18990[/TD]
[TD="align: right"]18940[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]12[/TD]
[TD="align: right"]108[/TD]
[TD="align: right"]19716[/TD]
[TD="align: right"]19666[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]13[/TD]
[TD="align: right"]116[/TD]
[TD="align: right"]19608[/TD]
[TD="align: right"]19558[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]14[/TD]
[TD="align: right"]133[/TD]
[TD="align: right"]19492[/TD]
[TD="align: right"]19442[/TD]
[TD][/TD]
[/TR]
[TR]
[TD="align: right"]15[/TD]
[TD][/TD]
[TD="align: right"]19359[/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD="align: right"]50[/TD]
[TD][/TD]
[/TR]
</tbody>[/TABLE]
in this example, in column C there are 14 iterations of subtracting 50 from each cell in column B, top down

but the value in C1 is =B1-C16(50).

C1 should = B1- (14x50)700=18542, as shown in D1.

each cell in column C should = the value of the prior row in column B, -50, as shown in 1st 3 rows of column D.

if xl allowed bottom up dragging and calculating, it would be simple, tho xtremely inefficient and prone to error. probably why it can't be done that way?

appreciate any assistance, and thanks for looking in on the post.

 

[Fluff]

How about
=B1-ROWS(B2:B$15)*C$16

 

[jetpack]

right as rain it is, mate. thanx so much, really appreciate your willingness to help. cheers!

 

[Fluff]

Glad to help & thanks for the feedback