Bubble Sizes In Bubble-Charts Macro

Im trying to create a simple 3D Bubble Chart macro, and as most people who've never dealt with this before (i think), i've hit a wall with BubbleSizes. I've attached the file im trying to get to work. The VBA is quite simple but an error occurs at BubbleSizes. I've read that BubbleSizes takes a different reference style than xValues and such, but haven't had any luck trying to change that. For those who just want to see the code without getting the file:

Sub EmbeddedChartFromScratch()
Dim myChtObj As ChartObject
Dim rngChtData As Range
Dim rngChtXVal As Range
Dim iColumn As Long
' make sure a range is selected
If TypeName(Selection) <> "Range" Then Exit Sub
' define chart data
Set rngChtData = Selection
' add the chart
Set myChtObj = ActiveSheet.ChartObjects.Add _
(Left:=250, Width:=375, Top:=75, Height:=225)
With myChtObj.Chart................................