Running Totals In Calc

[d1allan]

I often create spreadsheets in Calc with 2 number columns, one for a transaction, such as a debit or credit, then another which has a running balance. These are like checkbook registers. I use the sum function to add the previous balance to the new transaction and to create the new running total. I use the copy function to copy the formula and formats to a series of subsequent rows so that new transactions are automatically totalled.
The problems I have are:
A) The running total is entered into all lines for which I have copied the formula, even if no transaction entry has been entered. I would prefer that if no entry has been made, no total is entered on that row.
B) Sometimes I "Stack" these registers on one page. I'm not sure how many entries each will have, so I'd like to have the formula entered into the next line as each transaction is added. That way, I do not have to copy the formula to an arbitrary number of rows to make room for transactions which may never be entered.

I hope somebody understands my babble.
Thanks in advance for your help.
Allan

[JohnV]

First problem:
Assuming you numbers start in A1 I think this is what you want in B2 and below.
=IF(A2="";"";Sum(A$1:A2))

[d1allan]

That is exactly what I was looking for in problem #1. Excellent.
Thank you very much.