Getting script queried parameter values to pick from during an "on demand" workflow

Hi all,

I am trying to establish an "on demand" workflow in which a user can request a certain task. For that I am trying to give the initiator a drop down for a parameter with the available values based on a powershell query.

So basically the current policy script assigned in "Chose a script function to determine parameter values" looks like this.

function onInit($context)
$InitiatorDetails = get-qadobject ($Request.OperationInitiatorSid)
Get-QADUser $InitiatorDetails | Select memberof | % {$_.memberof -like "*_Eligible*"}

The result can be multi value and the initiator should be able to pick from these.

So now, I wouldn't write into this forum if that would work. If I run the workflow manually, I don't get the usual pop up with options like I would get if I am not using a script. 

Did anyone solve this requirement before already or is this just not possible to get using a script?