Powershell script monitor with encrypted password

Question

I have created a powershell script based monitor in my management pack and everything is ok but I can't get my credentials work inside the script. I want to open pssession to another computer with my credentials. I have triple checked that my pssession is
working because I can access it from powershell console.
This works perfectly at local server from PSconsole:
$EncryptedPassword ="01000000d08c9ddf0115d1118c7a00c04fc297eb01000000534b2....etc...etc..."
$pw = convertto-securestring -String $EncryptedPassword
$cred = new-object System.Management.Automation.PSCredential -argumentlist "MyDOMAIN\MyACCOUNT",$pw
$s = New-PSSession -ComputerName "MyServer" -Port MyPort -Credential $cred
But when I run the same lines inside my management pack the convertto-securestring
does nothing, it just wont convert the encrypted password to secure string!
I have tried this plain text method and it works
inside my management pack, but I don't want to use it because you can see the password in plain text:
ConvertTo-SecureString -String "myPlainTextPassword" -AsPlainText -Force
This is the $error variable, so it's basically says that I don't have anything in the password secure string variable because the convertion did not work for some reason:
The argument is null. Provide a valid value for the argument, and then try running the command again. Cannot process argument transformation on parameter 'Credential'. PromptForCredential Exception calling ".ctor" with "2" argument(s):
"Cannot process argument because the value of argument "password" is null. Change the value of argument "password" to a non-null value." The system cannot find the file specified. Exception calling "SecureStringToBSTR"
with "1" argument(s): "Value cannot be null. Parameter name: s" The system cannot find the file specified. Exception calling "SecureStringToBSTR" with "1" argument(s): "Value cannot be null. Parameter name: s"
The system cannot find the file specified. 
So is there some known issue with SCOM Agent / management pack when you are dealing with convertto-securestring
function with encrypted passwords?
I used these methods to encrypt the password: Technet article about encryption

Answer 1

I got it to work!
  <TypeDefinitions>
    <EntityTypes>
      <ClassTypes>
        <ClassType ID="MyClass" Accessibility="Public" Abstract="false" Base="Windows!Microsoft.Windows.LocalApplication" Hosted="true" Singleton="false" Extension="false"
/>
      </ClassTypes>
    </EntityTypes>
    <SecureReferences>
      <SecureReference ID="MyRunAsAccountProfile" Accessibility="Public" Context="System!System.Entity" />
    </SecureReferences>
<ScriptBody>param (
  [string]$Username,
  [string]$Password
$API = new-object -comObject "MOM.ScriptAPI" 
$PropertyBag = $API.CreatePropertyBag()
$cred = New-Object System.Management.Automation.PSCredential -Argumentlist @($Username,(ConvertTo-SecureString -String $Password -AsPlainText -Force))
$s = New-PSSession -ComputerName "myserver" -Credential $cred
Invoke-Command -Session $s -ScriptBlock { $service = Get-Service -Name Spooler}
$invcom = Invoke-Command -Session $s -ScriptBlock { $service.status}
Remove-PSSession -Id $s.Id
if ($invcom.Value -ne "Running") {
$PropertyBag.AddValue("State","ERROR") 
$outputLongLine = "Spooler Service is not running on target server!" 
$PropertyBag.AddValue("Description", $outputLongLine)
else {
$PropertyBag.AddValue("State","OK") 
$outputLongLine = "Spooler is Running on target server."
$PropertyBag.AddValue("Description", $outputLongLine) 
$PropertyBag</ScriptBody>
<Parameters>
<Parameter>
<Name>Username</Name>
 <Value>$RunAs[Name="MyRunAsAccountProfile"]/Domain$\$RunAs[Name="MyRunAsAccountProfile"]/UserName$</Value>
</Parameter>
<Parameter>
<Name>Password</Name>
<Value>$RunAs[Name="MyRunAsAccountProfile"]/Password$</Value>
</Parameter>