listbox.height setup will not work unless code is interrupted

I have a bizarre problem (to me). I must interrupt my code in VBA in order for the code to run correctly. Either, by setting a breakpoint or inserting a msgbox.
This has to do with setting the listbox .height on the form. The listbox is named “lstAttendees”

To interrupt the code, I use the line: MsgBox "height = " & .Height

If you run it without the msgbox the form will stay small and only show two employees. If I include the msgbox the form expands correctly.
Note: The form adjusts its height based on the listbox height and the listbox height is is based on the number of rows in the data field. There is also a maximum listbox height calculation to avoid problems when there are many columns.

Private Sub UserForm_Initialize()

Dim lastRow As Integer
Dim emplArr
Dim frmTop As Integer
Dim startRowCnt As Integer
Dim endRowCnt As Integer
Dim holder As String
Dim chbxTmp As Control
Dim topicRng As Range
Dim cbnOfSt As Integer
Dim tmpHgt As Integer
Dim topic As Range
    
cbnOfSt = 60

 lastRow = Range(Range("b2"), Range("b2").End(xlDown)).Count + 1

  frmTop = 80
  emplArr = Range("B2:B" & lastRow)
  
  'list the names
  With lstAttendees
        .List = Range(Range("b2"), Range("b2").End(xlDown)).Value
        .ListStyle = fmListStyleOption
        .MultiSelect = fmMultiSelectMulti
  End With

'!!!!!!!!!!!!!!!!!!!!!!!!!!PROBLEM AREA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
    'Listbox height
    With lstAttendees
        .Height = lastRow * 12.5
        'MsgBox "height = " & .Height  'Turn this on to see correct operation of listbox height
        
        ' set maximum size
        If .Height >= 300 Then
            .Height = 300
        End If
             
        'workaround the scrollbar bug
        '.IntegralHeight = false
        '.IntegralHeight = True
        .MultiSelect = fmMultiSelectSingle
        .MultiSelect = fmMultiSelectExtended
        
    End With

  'Form height
    Me.Height = lstAttendees.Height + 140
    Me.ScrollHeight = Me.Height
    Me.ScrollBars = fmScrollBarsVertical
    
    
    'Button Positions, move to bottom of form
    cbn_Enter_Data.top = Me.Height - cbnOfSt
    cbn_Close_Form.top = Me.Height - cbnOfSt
  
    'setup Topic Listbox
    Set topicRng = Range("topics")
   
    'setup Topic Listbox (from forums)
    For Each topic In topicRng
        If Not topic.Value = "(Required)" Then
            With Me.cbx_Topic_Choice
                .AddItem topic.Value
            End With
        End If
    Next topic

End Sub

THANKS FOR LOOKING!
Robert

thanks Richard, that works. But it sounds like changing the form object during the initialization event is "cough" bad form.
Maybe I should be constructing the form differently. Ill have to think about that.
Thanks again for helping me out. If I were on your side of the Atlantic I would buy you a pint! Fullers would be my choice.