Writing selected items from listbox to textbox

[lotus18]

Hello world!!!

How can I write all the selected item of the listbox to a textbox? For e.g. I have these items from a listbox:

-rey
-john
-jane
-mike
-ken
-blen

If I selected rey and jane, the output of the textbox should be rey, jane else the output is All
By the way, my listbox's style is 1-Checkbox.

This is my sample code

Private Sub cmdOK_Click()
    If chkAll.Value = 1 Then
        txtName.Text = "All"
    Else
        txtName.Text = lstNames.Text
    End If

Please guide me. thanks