Graph that's adding values and skipping blanks

Let's say i want to make a graph showing how much i have payed on my car loan.

I have a table looking something like this that i add my current net worth a few times per month.
So i get a nice chart about how my economy has been.

Date	In bank atm	Paying to car loan
10 Jan	1000	5000
12 Jan	980	0
17 Jan	3500	0
19 Jan	3400	4500
25 Jan	3000	0
5 Feb	2500	500
10 Feb	2200	3500

But now i want to have a chart that adds up all payments i made to a loan, so the graph gets higher and higher (and skip the blanks).
Is that possible, and if so, how?

I would add a helper column that performs the cumulative summation, then use that column in the chart.

1) The helper column might have a formula like =SUM(C$2:C2) and copy down (note the mix of relative and absolute references for easy copying).
2) For the chart, select the date column and the helper column -> insert chart -> desired chart type -> desired sub chart type.

Unless Excel really messes up the chart, that should be close to what you describe.

Not sure I understand. If I understand, that should simply require adding an IF() function around the SUM() function with an appropriate "decision logic" =IF(should this cell be blank?,"",SUM(...)). Can I assume that you are already familiar with the IF() function and how to formulate the required logic condition statement?