Windows Form with PowerShell - getting selected items from Listbox

Question

Windows Form with PowerShell - getting selected items from Listbox. I have script which take inputs from Excel and load into list box called available Clients. Then depending on requirement remove clients from available list to excluded list and whatever final remains in available list should be displayed. .

Here is the part of script:

$btn_Proceed.Add_click({

$selecteditems = $lb_available.Items

Write-Host "Availabe clients for Patching are $selecteditems" 

$frm_patching.Close()
})

I am have trouble to list those available line and pass it to another script to execute.