Fixing range of y values for graph with VBA - excel

Question

I have written the following code to display a basic line graph.
Sub addchart()
If ActiveSheet.ChartObjects.Count > 0 Then
ActiveSheet.ChartObjects.Delete
End If
Dim ws As Worksheet
Dim ch As chart
Dim dt As Range
Dim i As Integer
i = Cells(Rows.Count, "M").End(xlUp).Row
Set ws = ActiveSheet
Set dt = Range(Cells(2, 14), Cells(i, 14))
Set ch = ws.Shapes.AddChart2(Width:=1300, Height:=300, Left:=Range("a13").Left, Top:=Range("a13").Top).chart
With ch
.SetSourceData Source:=dt
.ChartTitle.Text = "Deflection Curve"
.ChartType = xlLineMarkers
End With
End Sub
But the trouble with this is that the range of Y axis adjusts itself according to the data automatically. I want to fix this range so that the change in the graph is noticeable.
For example, the following two graphs vary in the range of values they cover but they look basically the same because the y axis is adjusting itself. One goes from 0 to -9 and the other from 0 to -25. If I can fix the range to say 0 to -30, the difference in the two graphs would be more apparent.

Answer 1

With ch.Axes(xlValue)
.Minimumscale = -30
.Maximumscale = 0
End with
Relevant links:
Chart.Axes method
Axis Object

Answer 2

Thanks to Spencer, the following code gets the result I want
Sub addchart()
If ActiveSheet.ChartObjects.Count > 0 Then
ActiveSheet.ChartObjects.Delete
End If
Dim ws As Worksheet
Dim ch As chart
Dim dt As Range
Dim i As Integer
i = Cells(Rows.Count, "M").End(xlUp).Row
Set ws = ActiveSheet
Set dt = Range(Cells(2, 14), Cells(i, 14))
Set ch = ws.Shapes.AddChart2(Width:=1300, Height:=300, Left:=Range("a13").Left, Top:=Range("a13").Top).chart
With ch
.SetSourceData Source:=dt
.ChartTitle.Text = "Deflection Curve"
.ChartType = xlLineMarkers
End With
With ch.Axes(xlValue) 'fixing range of values
.MinimumScale = -30
.MaximumScale = 0
End With
End Sub