Scheduling adding computers to and from an AD security group

Hi All,

I'm looking to add a number of computers to a security group on the last Monday of every month and then remove them 2-3 days later but having a little difficulty so hoping someone can point me in the right direction,

I have this script to check if the day is the last Monday of the month

function Get-LastMondayOfMonth([DateTime] $d) {   

    $lastDay= new-objectDateTime($d.Year, $d.Month, [DateTime]::DaysInMonth($d.Year, $d.Month))

    $diff= ([int] [DayOfWeek]::Monday) - ([int] $lastDay.DayOfWeek)

    if ($diff-ge0) {

        return $lastDay.AddDays(- (7-$diff))

    }

    else {

        return $lastDay.AddDays($diff)

    }   

}

I now need to know how i pass the results of this to a workflow that already adds the computers to the correct group just that its not automated yet....

Thanks

Alex