Tushar Mehta wrote:
Addressing your requests in reverse order...

Usually there is no need to select and/or activate objects.

Iterating through a collection with the For...Each loop removes the
need to id individual objects.

The For...Each loop also lets one go through each object in a
collection. In this case, there are two collections that need to be
addressed. The sheets in a workbook and the chartobjects in a sheet.

The code below addresses all three of your concerns:

Option Explicit
Option Base 0

Sub doOneChart(aChart As Chart)
With aChart.Axes(xlCategory)
.MinimumScale = Range("param!i35").Value2
.MaximumScale = Range("param!i45").Value2
End With
End Sub
Sub FixAllChartsInActiveWorkbook()
Dim aSheet As Object, aChartObj As ChartObject
For Each aSheet In ActiveWorkbook.Sheets
If TypeOf aSheet Is Chart Then doOneChart aSheet
If TypeOf aSheet Is Chart Or TypeOf aSheet Is Worksheet Then
For Each aChartObj In aSheet.ChartObjects
doOneChart aChartObj.Chart
Next aChartObj
End If
Next aSheet
End Sub


I am grateful to you all for your prompt reply.

The variation to Jerry's code introduced by Andy is, in
effect, necessary. Tushar's macro stops executing when it
gets to the 3D-charts.

On the other hand, only Tushar's macro tries executing in
all sheets. So I have a mix of the two:

Sub Macro1()
minim = Range("param!i35").Value2
maxim = Range("param!i45").Value2
For Each aSheet In ActiveWorkbook.Sheets
For Each ch In aSheet.ChartObjects
Select Case ch.Chart.ChartType
Case xlXYScatter, xlXYScatterLines,
xlXYScatterLinesNoMarkers, _
xlXYScatterSmooth, xlXYScatterSmoothNoMarkers
With ch.Chart.Axes(xlCategory)
.MinimumScale = minim
.MaximumScale = maxim
End With
End Select
Next ch
Next aSheet
End Sub

And it works ... too well. But that's my fault. I had
overlooked the fact that 33 of the scatter graphs (11 in 3
sheets) have dates on the x-axis, and must not be modified.
I am sorry about that. So how do I exclude them from macro
execution ? Two ways come to my mind:
- modify their type and exclude the type. I am referring to
the types mentioned in the code above (which I don't
understand): xlXYScatter, xlXYScatterLines,
xlXYScatterLinesNoMarkers, xlXYScatterSmooth,
xlXYScatterSmoothNoMarkers
- exclude them by name.
In any case, I wouldn't know how to do it and still need help.

What about modifying a chart's name ?