Excel VBA: Programmatically setting X,Y,Z values for chart generation - vba

Question

The following code succesfully generates an XY scatter plot with dynamically changing ranges. However, the hurdle I can't get over is how to programmatically set the x,y,z values for the scatterplot to generate a bubble chart. I've made attempt at doing so(as you can see in the code) but it doesn't work.
Any helps is appreciated
dim a as long
dim b as long
dim i as long
dim m as long
dim j as long
For i = 2 To lastrow
If Cells(i, "A") = "Regression #" & m & " Output" Then
a = i 'save regression #1 row number, where it begins
For j = 2 To a
If Cells(j, "A") = "Regression #" & m + 1 & " Output" Then
b = j
End If
Next j
Set rngx = Range(Cells(b + 1, 2), Cells(a - 1, 2))
Set rngy = Range(Cells(b + 1, 7), Cells(a - 1, 7))
Set rngz = Range(Cells(b + 1, 8), Cells(a - 1, 8))
Sheets("Chart Table").Shapes.AddChart.Select
ActiveChart.ChartType = xlBubble
ActiveChart.SetSourceData Source:=Union(rngx, rngy, rngz)
With ActiveChart.SeriesCollection.NewSeries
'.Name = ActiveSheet.Range("B2:B13")
.value = rngy
.xvalues = rngx
.BubbleSizes = rngz
End With
With ActiveChart
.SetElement (msoElementChartTitleAboveChart)
.Legend.Delete
.ChartTitle.Select
.ChartTitle.Text = Cells(a, 1).Value
End With
Else
End If
Next i
For example, if I have just one row of data(one x, one y, one z) - then I want Excel to know that it means there's only one bubble. Right now it reads it as 3 separate bubbles, disregarding the fact there's a bubble sizing element

Answer 1

If the union of rngx, rngy, and rngz is a contiguous range, it works fine. Since these ranges are separated by several columns, your SetSourceData command is incomplete, and treats their union as a set of Y values, and uses the default (1, 2, 3) as X values and (1, 1, 1) as bubble sizes.
However, this small change fixes your code:
ActiveChart.SetSourceData Source:=Union(rngx, rngy, rngz), PlotBy:=xlColumns