Call a function inside a Script Block powershell

I have code to register a Tentacle in Octopus and I want to call a Function called RunCommand inside the Scriptblock. It keeps failing when I try to call it inside the Scriptblock. I am reading my data from a csv file but just cant figure out how to call the function inside the Scritblock. Anyone know how this is done. As you can see from the code I am calling the RunCommand function but it keeps failing. I have come acress using the function: call but that does not work either. Please help.

function RunCommand{
Param(
  [string]$myCommand,
  [string]$myArgs
  )

$process = Start-Process -FilePath $myCommand -ArgumentList $myArgs -Wait -PassThru
if ($process.ExitCode -eq 0){
    Write-Host "$myCommand successful"
} else {
    Write-Host "$myCommand failed"
}  
return $process.ExitCode

function DeployTentacle{

#Read data from a csv file
$csv = Import-Csv -Path "C:\Users\adm_qvl6\Documents\RegisterTentacle.csv"

$csv | ForEach-Object {
    $ServerName = $($_.ServerName)
    $WorkerName = $($_.WorkerName)
    $Port = $($_.Port)  
    $Space = $($_.Space)    
    $Pool = $($_.Pool)
    $TentacleSource = $($_.TentacleSource)
    $TentacleDestination = $($_.TentacleDestination)
    $TentacleInstallPath = $($_.TentacleInstallPath)
    $TentacleWorkFolder = $($_.TentacleWorkFolder)
    $APIKey = $($_.APIKey)
    $OctopusURL = $($_.OctopusURL)
    $OctopusThumbprint = $($_.OctopusThumbprint)

    Invoke-Command -ComputerName $ServerName -ScriptBlock{

    param($WorkerName, $Port, $Space, $Pool, $TentacleSource, $TentacleDestination, $TentacleInstallPath, $TentacleWorkFolder, $APIKey, $OctopusURL, $OctopusThumbprint)

        $args="create-instance --instance `"$WorkerName`" --config `"$TentacleWorkFolder\Tentacle.config`""
        $rc = RunCommand $TentacleInstallPath $args

        $args="new-certificate --instance `"$WorkerName`" --if-blank"
        $rc = RunCommand $TentacleInstallPath $args

        $args="configure --instance `"$WorkerName`" --reset-trust"
        $rc = RunCommand $TentacleInstallPath $args

        $args="configure --instance `"$WorkerName`" --app `"$TentacleWorkFolder\Applications`" --port `"$Port`" --noListen `"False`""
        $rc = RunCommand $TentacleInstallPath $args

        $args="configure --instance `"$WorkerName`" --trust $OctopusThumbprint"
        $rc = RunCommand $TentacleInstallPath $args

        $args="service --instance `"$WorkerName`" --install --stop --start"
        $rc = RunCommand $TentacleInstallPath $args

        $args="register-worker --space `"$Space`" --instance `"$WorkerName`" --server `"$OctopusURL`" --apiKey=`"$APIKey`" --workerpool=`"$Pool`" --comms-style TentaclePassive --force"
        $rc = RunCommand $TentacleInstallPath $args

        $args="service --instance `"$WorkerName`" --install --stop --start"
        $rc = RunCommand $TentacleInstallPath $args    

    } -ArgumentList $WorkerName, $Port, $Space, $Pool, $TentacleSource, $TentacleDestination, $TentacleInstallPath, $TentacleWorkFolder, $APIKey, $OctopusURL, $OctopusThumbprint

} }

With invoke-command you are creating a session to another host. You don't push your complete script into the session but only the scriptblock. So you've got to define your function INSIDE of the scriptblock to use it inside it.

invoke-command -scriptblock{
    function newfunc{
        #do something
    }
    newfunc
}