Dynamically create column if a particular column does not exist within the data

Hi,

This code works fine for me.  I saved all 3 files on a desktop folder named Data.  From all 3 files i deleted the first row (where the file name was mentioend).  Here's the M query

let
    Source = Folder.Files("C:\Users\Ashish\Desktop\Data"),
    #"Removed Other Columns" = Table.SelectColumns(Source,{"Content"}),
    #"Added Custom" = Table.AddColumn(#"Removed Other Columns", "Custom", each Excel.Workbook([Content])),
    #"Removed Columns" = Table.RemoveColumns(#"Added Custom",{"Content"}),
    #"Expanded Custom" = Table.ExpandTableColumn(#"Removed Columns", "Custom", {"Name", "Data", "Item", "Kind", "Hidden"}, {"Name", "Data", "Item", "Kind", "Hidden"}),
    #"Removed Other Columns1" = Table.SelectColumns(#"Expanded Custom",{"Data"}),
    #"Added Custom1" = Table.AddColumn(#"Removed Other Columns1", "Custom", each Table.PromoteHeaders([Data])),
    #"Removed Columns1" = Table.RemoveColumns(#"Added Custom1",{"Data"}),
    #"Expanded Custom1" = Table.ExpandTableColumn(#"Removed Columns1", "Custom", {"Month #", "ID", "Annual", "Quarterly", "Monthly", "Total", "Semi Annual "}, {"Month #", "ID", "Annual", "Quarterly", "Monthly", "Total", "Semi Annual "}),
    #"Reordered Columns" = Table.ReorderColumns(#"Expanded Custom1",{"Month #", "ID", "Annual", "Semi Annual ", "Quarterly", "Monthly", "Total"}),
    #"Changed Type" = Table.TransformColumnTypes(#"Reordered Columns",{{"Month #", Int64.Type}, {"ID", Int64.Type}, {"Annual", Int64.Type}, {"Semi Annual ", Int64.Type}, {"Quarterly", Int64.Type}, {"Monthly", Int64.Type}, {"Total", Int64.Type}})
in
    #"Changed Type"

The result is