pivot charts in excel changing layout

[etaf]

I have been putting together some pivot table charts in excel (for m
brother who has excel2000, I have excel2003 - both versions show th
same problem).
the charts default to a bar chart.
I have set up a custom chart which has 1 bar and 1 line - i have als
set it to default.
However, every time the chart is updated or change - ot changes back t
the barchart only.

so say we have 5 periods of data and on the chart we look at period 1
with a bar/line combo with clear background graph, when we change t
period 2 on the pivot the chart changes to just a barchart with a gra
background.

how can i set our custome chart to stay default.....

thank