$timeframes = 1,5,15

foreach ($timeframe in $timeframes)
{
    
    $maxDataBars = switch ( $timeframe )
    {
        1  { 200000 }
        5  { 55000 }
        15 { 35000 }        
    }
    
    $datafile = ".\mydata\${timeframe}.json"        
    
    $command = "node .\bin\gen.js `
               --settings .\forex.ini `
               --period = $timeframe `
               --data_file = $datafile `
               --max_data_bars = $maxDataBars"

    start cmd -ArgumentList "/k $command"
}