And on Big Mike's Trader discussion forum: http://www.bigmiketrading.com/tradestation-multicharts-easylanguage-programming/3502-global-variables-gv-easylanguage-tradestation-multicharts.html
Global variables can be used in backtesting only in Portfolio BacktesterTrader: http://www.multicharts.com/trading-software/index.php/Spread_and_Pair_Trading#Pair_Trading_in_Backtesting