Subtracting Previous Cells?

[ExcelChrisAcc]

Let's say that my chart looks like this
___A____B
1|120___X
2|430___X
3|500___X
4|324___X
5|290___X

So how would I make it so that a column B computes this
B1 = (A4-A5)
B2 = (A3-A4)
B3 = (A2-A3)
B4 = (A1-A2)
I know this could be done manually, but I have a larger array of numbers which would make it impractical. Thank you very much for the help!

 

[DavidCoop]

Try this - all you have to vary is the last cell of the COUNT function.

=INDIRECT("A"&COUNT($A1:$A$5)-1)-INDIRECT("A"&COUNT($A1:$A$5))

Rgds David

 

[ExcelChrisAcc]

Thank you for the help, but I got the hang of it.