Dynamic Heat Map

I need to create many XY charts in a VBA macro. For each chart, I need to select a particular column for the X dimension, and a particular column for the Y dimension. When I use a named range to define the X and Y columns, my macro works fine for those instances when the X comes first. However, if my desired Y dimension comes first, I cannot find a way to correctly select these.

The context is such that my spreadsheet always has the same data fields in the same columns, but the numbers of rows vary. In addition, I need to dynamically select which rows to use, based on the values in the columns to be plotted. I’ve figured out how to do this within the macro, except for those instances when the Y column comes before the X. An example when this works:

Sheets("Raw").Select
Names.Add Name:="newRange", RefersTo:="=$K13" & ":" & "$K" & FirstBias _
& ",$M13" & ":" & "$M" & FirstBias, Visible:=True Range("K1").Activate
Charts.Add
ActiveChart.ChartType = xlXYScatterLines
ActiveChart.SetSourceData Source:=Sheets("Raw").Range("newRange"), PlotBy:=xlColumns
ActiveChart.Location Where:=xlLocationAsNewSheet, Name:="Field10vsField12"
With ActiveChart
.HasTitle = True........................