One way of getting dynamic charts is with AutoFilter. Have all the data on
one worksheet with columns to represent Regional level, Zonal level and City
level. All rows of data would be Regional, Zone name against the data for
specific zones and City name against data for each city.

Now depending on how your chart is set up, you can either select all of the
data for the chart and then set filters for the Region, Zone or City.
Alternatively you can use the SUBTOTAL function and set the chart on the
subtotal line only and the subtotals are dynamic with the AutoFilter
selections. Suggest that you look up subtotal function in help for the
parameters representing the various mathematical calculations.

One other tip is to leave six or so lines above the column headers and then
Freeze the panes so that the column headers and rows above are always
displayed irrespective of how far you scroll down the screen. You can then
place the subtotals in this area at the top of the screen and they are always
visible and never have to be moved as you add rows of data. (You need to use
all of the rows to the bottom of the worksheet in the subtotal functions.)

I am sure if you google excel charts and autofilter you will find some
examples.

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Regards,

OssieMac