Variable Expansion

i'm working on exchange management shell script, i've got simple powershell related question. let's i've got following script:

$recipient = read-host "enter recipient's email address"

$sender = read-host "enter sender's email address"

$start = read-host "enter start date and time in the format 2/12/2009 9:00:00 am"

$end = read-host "enter end date and time in the format 2/12/2009 9:30:00 am"

if($recipient -ne "")

{$recipientarr = "-recipient", $recipient

$recipientarr_join = [string]::join(" ", $recipientarr)

$argsarr = $recipientarr_join + " "}

if($sender -ne "")

{$senderarr = "-sender", $sender

$senderarr_join = [string]::join(" ", $senderarr)

$argsarr += $senderarr_join + " "}

if($start -ne "")

{$startarr = "-start", $start

$startarr_join = [string]::join(" ", $startarr)

$argsarr += $startarr_join + " "}

if($end -ne "")

{$endarr = "-end", $end

$endarr_join = [string]::join(" ", $endarr)

$argsarr += $endarr_join}

get-exchangeserver | where {$_.ishubtransportserver -eq $true -or $_.ismailboxserver -eq $true} |  get-messagetrackinglog $argsarr

this isn't working because get-messagetrackinglog doesn't $argsarr. $argsarr variable @ end -recipient user1@email.com -sender user2@email.com -start "2/12/2009 9:00:00 am" -end "2/12/2009 9:30:00 am" depending on how questions answered. if run:

get-exchangeserver | where {$_.ishubtransportserver -eq $true -or $_.ismailboxserver -eq $true} |  get-messagetrackinglog -recipient user1@email.com -sender user2@email.com -start "2/12/2009 9:00:00 am" ` -end "2/12/2009 9:30:00 am"

i correct output. how script correctly recognize $argsarr variable @ end it's manually putting in arguments? thought might expansion issue , have tried using "'$($argsarr)'" , $($argsarr), didn't work. give me clue? i'm sure stupidly easy, haven't been able find solution.

 invoke-expression "get-messagetrackinglog $argsarr"

Windows Server  >  Windows PowerShell