New-Mailbox / Set-CalendarProcessing / Set-Mailbox /Add-MailboxPermission --> for multiple users

Hey Guys,

time to admit defeat and post on the forum..

($RoomsAndMember.Users).Split(";")

seemed to work for all but the last command:

Add-MailboxPermission -Identity $RoomsAndMember.Alias -User ($RoomsAndMember.Users).Split(";") -AccessRights FullAccess

it gets the below error:

Cannot process argument transformation on parameter 'User'. Cannot convert the "System.Collections.ArrayList" value of type "System.Collections.ArrayList" to type
"Microsoft.Exchange.Configuration.Tasks.SecurityPrincipalIdParameter".
    + CategoryInfo          : InvalidData: (:) [Add-MailboxPermission], ParameterBindin...mationException
    + FullyQualifiedErrorId : ParameterArgumentTransformationError,Add-MailboxPermission
    + PSComputerName        : SERVERNAME

Ive done some googling and some people have mentioned Loops to fix this issue but I haven't figured out how to apply any of the scripts to my situation.

Full script below, I have copied other people scripts, haven't yet found a way to find the time to pick up a PS book and study the fundamentals:

$ExchangeSession = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri http://SERVERNAME/powershell
Import-PSSession $ExchangeSession
Set-Location "C:\DATA\OneDrive\Work\Tech_Support\Scripts\Exchange - Create Exchange Room Add members"

$ExcelWB = new-object -comobject excel.application
    $Workbook = $ExcelWB.Workbooks.Open("C:\DATA\OneDrive\Work\Tech_Support\Scripts\Exchange - Create Exchange Room Add members\RoomsAndMembers.xlsx")
    $Workbook.SaveAs("C:\DATA\OneDrive\Work\Tech_Support\Scripts\Exchange - Create Exchange Room Add members\RoomsAndMembers.csv",6)
    $Workbook.Close($false)
    $ExcelWB.quit()
    $RoomsAndMembers = import-csv .\RoomsAndMembers.csv


ForEach ($RoomsAndMember in $RoomsAndMembers) {
    $RoomsAndMember
   New-Mailbox -Database "EXDB-06" -Name $RoomsAndMember.DisplayName -DisplayName $RoomsAndMember.DisplayName -UserPrincipalName $RoomsAndMember.UserPrincipalName -PrimarySmtpAddress $RoomsAndMember.PrimarySmtpAddress -Room -OrganizationalUnit "OU=Resource Mailboxes,OU=Production,DC=water,DC=internal" -Alias $RoomsAndMember.Alias -Office $RoomsAndMember.OfficeLocation
   Start-Sleep 15
   Set-CalendarProcessing -Identity $RoomsAndMember.Alias -ResourceDelegates ($RoomsAndMember.Users).Split(";") -BookInPolicy ($RoomsAndMember.Users).Split(";") -AutomateProcessing AutoAccept -MaximumDurationInMinutes "50400" -BookingWindowInDays "180" -DeleteSubject $false
   Start-Sleep 5
   Set-Mailbox -Identity $RoomsAndMember.Alias -GrantSendOnBehalfTo ($RoomsAndMember.Users).Split(";")
   Start-Sleep 5
   Add-MailboxPermission -Identity $RoomsAndMember.Alias -User ($RoomsAndMember.Users).Split(";") -AccessRights FullAccess
        }

Thank you very much in advance :) even pointing me to an explanation will suffice hopefully :)