Nesting dynamic parameters in PowerShell - powershell

Question

I am working on a function that will insert a row into a SQL database. It is basically a simple change log to help me track what is changed on my various SQL instances. As part of this, I want to have the following parameters:
Timestamp
Server
Instance
Change
I've got the Timestamp, Change, and Server all figured out, but the Instance is giving me some trouble. The Server parameter is dynamic, as it pulls a list of SQL servers from my inventory. I then want the value of that parameter to be used in another dynamic parameter, which pulls a list of the instances that are on that server (also from my inventory). Here is what I have for the dynamic portion:
DynamicParam {
if (!(Get-Module sqlps)){ Pop-Location; Import-Module sqlps -DisableNameChecking; Push-Location }
$inventoryinstance = 'ServerName'
$newparams = New-Object System.Management.Automation.RuntimeDefinedParameterDictionary
$server_query = 'SELECT [Name] FROM [ServerInventory].[dbo].[Servers] WHERE [TypeID] = 1 ORDER BY [Name]'
$servers = Invoke-Sqlcmd -serverinstance $inventoryinstance -query $server_query -connectiontimeout 5
# Populate array
$serverlist = #()
foreach ($servername in $servers.Name) {
$serverlist += $servername
}
$attributes = New-Object System.Management.Automation.ParameterAttribute
$attributes.ParameterSetName = "__AllParameterSets"
$attributes.Position = 1
$attributes.Mandatory = $true
$attributes.HelpMessage = "The server the change was made on"
# Server list parameter setup
if ($serverlist){ $servervalidationset = New-Object System.Management.Automation.ValidateSetAttribute -ArgumentList $serverlist }
$serverattributes = New-Object -Type System.Collections.ObjectModel.Collection[System.Attribute]
$serverattributes.Add($attributes)
if ($serverlist){ $serverattributes.Add($servervalidationset) }
$serverob = New-Object -Type System.Management.Automation.RuntimeDefinedParameter("Server", [String], $serverattributes)
$newparams.Add("Server", $serverob)
$instance_query = "SELECT [Name] FROM [ServerInventory].[dbo].[SQLInstances] WHERE [ServerID] = (SELECT [ServerID] FROM [ServerInventory].[dbo].[Servers] WHERE [Name] = '$($PSBoundParameters.Server)')"
$instances = Invoke-Sqlcmd -serverinstance $inventoryinstance -query $instance_query -connectiontimeout 5
# Populate array
$instancelist = #()
foreach ($instancename in $instances.Name) {
$instancelist += $instancename
}
$attributes = New-Object System.Management.Automation.ParameterAttribute
$attributes.ParameterSetName = "__AllParameterSets"
$attributes.Position = 2
$attributes.Mandatory = $false
$attributes.HelpMessage = "The instance the change was made on, do not specify for server-level changes"
# Server list parameter setup
if ($instancelist){ $instancevalidationset = New-Object System.Management.Automation.ValidateSetAttribute -ArgumentList $instancelist }
$instanceattributes = New-Object -Type System.Collections.ObjectModel.Collection[System.Attribute]
$instanceattributes.Add($attributes)
if ($instancelist){ $instanceattributes.Add($instancevalidationset) }
$instanceob = New-Object -Type System.Management.Automation.RuntimeDefinedParameter("Instance", [String], $instanceattributes)
$newparams.Add("Instance", $instanceob)
return $newparams
}
Everything seems to be working, except the value for the instance variable doesn't autocomplete. Is it possible to use the value of one dynamic parameter to generate another?