VBA: How to update a trendline label in excel - vba

Question

sometimes it happens that the trendline label in excel isn't updated when I changed the graph-data. Therefore I want to update via VBA. I want to do it for all existing trendlines in all sheets and charts.
My code until now doesn't work. You will find the error in the comment.
Sub Auto_Open()
Debug.Print "Start"
Dim oChart As ChartObject, nSheet As Integer, nChart As Integer
nSheet = 1
Do While nSheet <= Sheets.Count
nChart = 1
Do While nChart <= Sheets(nSheet).ChartObjects.Count
nSeriesCollection = 1
'Debug.Print Sheets(nSheet).ChartObjects(nChart).SeriesCollection.Count
'Error in next line
Do While nSeriesCollection <= Sheets(nSheet).ChartObjects(nChart).SeriesCollection.Count
Debug.Print "nSheet: " & nSheet & " nChart: " & nChart
Set oChart = Sheets(nSheet).ChartObjects(nChart)
oChart.Activate
'Next line has to changed too
ActiveChart.SeriesCollection(1).Trendlines(1).Select
With Selection
.DisplayRSquared = False
.DisplayEquation = False
.DisplayRSquared = True
.DisplayEquation = True
End With
nSeriesColletion = nSeriesColletion + 1
Loop
nChart = nChart + 1
Loop
nSheet = nSheet + 1
Loop
End Sub
########################################################################
There is a run-time error '438'. Object doesn't support this property or method in the line with the error comment.

Answer 1

There is error in
ActiveChart.SeriesCollection(1).Trendlines(1).Select
Change it to:
ActiveChart.SeriesCollection(1).Trendlines(1).DataLabel.Select

Answer 2

Here is the solution:
:)
Sub Auto_Open()
Debug.Print "###########################################"
Debug.Print "Start"
Dim oChart As ChartObject, nSheet As Integer, nChart As Integer
nSheet = 1
Do While nSheet <= Sheets.Count
Debug.Print "Sheet: " & nSheet
nChart = 1
Do While nChart <= Sheets(nSheet).ChartObjects.Count
Debug.Print " ChartObjects: " & nChart
nSeriesCollection = 1
Do While nSeriesCollection <= Sheets(nSheet).ChartObjects(nChart).Chart.SeriesCollection.Count
Debug.Print " SeriesCollection: " & nSeriesCollection
Sheets(nSheet).ChartObjects(nChart).Chart.SeriesCollection(nSeriesCollection).Trendlines(1).DisplayEquation = True
nSeriesCollection = nSeriesCollection + 1
Loop
nChart = nChart + 1
Loop
nSheet = nSheet + 1
Loop
End Sub

Answer 3

I'm waaay late to the game, but for posterity's sake...
I think the error can be avoided by using for each ... next construct rather than the do while ... loop option and eliminating the unnecessary Select(ellipses is other misc code):
...
For Each oSheet In Sheets
iSheet = iSheet + 1 'if an indexing is needed'
...
For Each oChart In oSheet.Charts
iChart = iChart + 1 'if an indexing is needed'
...
For Each oSeries In oChart.SeriesCollection
iSeries = iSeries + 1 'if an indexing is needed'
For Each oTrend In oSeries.Trendlines
With oTrend
.DisplayEquation = False
.DisplayRSquared = False
'the next statement often assures eq is updated
'unsure if there is a more reliable solution
DoEvents
.DisplayEquation = True
.DisplayRSquared = True
End With
Next oTrend
...
Next oSeries
...
Next oChart
...
Next oSheet