Multiple Selection From ListBox

[HTSCF Fareha]

Moving on from the ComboBox method, trying to enable selection of more than one from a ListBox is throwing up

Run-Time Error '94': Invalid use of null

Private Sub UserForm_initialize()

Dim myArray     As Variant
    myArray = Split("- Select One Or More -|Requires further investigation|Urgent review|" _
            & "Manageable risk|For Noting Only", "|")
    'Use List method to populate listbox
    ListBox1.List = myArray
    ListBox1.ListIndex = 0
    
'Redefine list for reason for threat level
    'Select threat level
    'Create list of grades for threat
    myArray = Split("- Select -|High|Medium|Low", "|")
    'Use List method to populate listbox
    ComboBox2.List = myArray
    ComboBox2.ListIndex = 0
    'Use List method to populate listbox
    ComboBox3.List = myArray
    ComboBox3.ListIndex = 0
    'Use List method to populate listbox
    ComboBox4.List = myArray
    ComboBox4.ListIndex = 0
    'Use List method to populate listbox
    ComboBox5.List = myArray
    ComboBox5.ListIndex = 0 

 lbl_Exit:
    Exit Sub
End Sub


Private Sub ListBox1_Change()
    If ListBox1.ListIndex > 0 Then
        TextBox2.Text = ListBox1.Value
    End If
    Select Case ListBox1.Value
        Case "Requires further investigation":
            TextBox2.Text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. In rhoncus, lorem et fringilla dictum, orci orci posuere lacus, ut auctor libero neque non purus. Fusce a commodo ligula."
        Case "Urgent review":
            TextBox2.Text = "Proin sed nisl enim. Cras in nisl tempus, scelerisque mi id, vulputate arcu. Duis nec mi ac lorem pretium semper."
        Case "Manageable risk":
            TextBox2.Text = "Fusce eu nisi sollicitudin, pharetra nibh sed, vestibulum neque. Praesent a auctor turpis. Mauris posuere vitae justo ac mollis."
        Case "For Noting Only":
            TextBox2.Text = "Sed eu eros ipsum. Ut posuere id magna eu sollicitudin. Nunc suscipit tempor egestas. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos."
        Case Else
            TextBox2.Text = ""
    End Select
    
lbl_Exit:
    Exit Sub
End Sub

I've highlighted where it falls over.

I want to allow the user to be able to select none, one or more from the list (I intend to add more options to the list once this is working).

As an aside, what is the maximum amount of characters I could use for TextBox2.Text ?

Thanks!