Don't use vba for that. You can use vba in Ruby like the example below illustrates but there are Ruby gems that do all you want easier and better, eg take a look at the Roo gem.
And since it is csv you could just join the files and save it als one big csv file.
Excel will have no trouble opening the joined csv.
You don't even need the csv gem (included in the core libraries) for that unless you need managing the data.
require 'win32ole'
excel = WIN32OLE.new('Excel.Application')
excel.visible = true
workbook = excel.Workbooks.Add();
worksheet = workbook.Worksheets(1);
worksheet.Range("A1:D1").value = ["North","South","East","West"];
worksheet.Range("A2:B2").value = [5.2, 10];
worksheet.Range("C2").value = 8;
worksheet.Range("D2").value = 20;
range = worksheet.Range("A1:D2");
range.select
chart = workbook.Charts.Add;
workbook.saved = true;
Here an exampel of using Roo
require 'roo'
w1 = Roo::Spreadsheet.open( "C:/Ruby193/test/roo/2.csv" )
w1.each_with_pagename do |name,sheet|
puts name, sheet.row(1)
end