ExcelBanter - Line Charts - Is this possible?

I have developed a budget tracking tool in Excel and one of the reports I
need to generate is a line chart which displays a Cumulative Forecast Amount
by month and a Cumulative Actual Spend by month.

I have used a table with formulas to calculate the figures for each month.
Below is an example:

JUL AUG SEP OCT NOV DEC
CFA $1830 $3490 $5690 $6100 $8000 $8600
CAS $1570 $2274 $2274 $2274 $2274 $2274

As you can see, the Cumulative Actual Spend figures for Sept onwards are
identical as we haven't completed those months.

Currently, my Line Chart shows a line for CFA for each month of the year,
and another line for CAS also for each month of the year. Of course, in the
above example, the CAS line flatlines for the entire period of Aug to Dec.

What I want is a way for the line chart only to display the CAS line up to
and including the current month. In other words, this line will be shorter
for 11 months of the year, only growing at the end of each month.

Is there some way to automate this via chart settings, formulas, and/or
programming?

APOLOGY
I have posted this question to the Excel Charts, Excel Programming and Excel
Worksheet Functions newsgroups as I did not know the full USENET designation
to "cross-post" this properly. Can someone advise me for future reference?

Thanks in advance.

Your help would be most appreciated.

Joe.
--
If you can measure it, you can improve it!