Selective values to fill combobox

I need to show values in combobox that have no values to the left of them. It is a calendar with dates as the first column and then either events or blanks in the next column. For my form I want only the dates with blanks to show in the combobox. So far I have this code, but I'm having trouble adding a loop as it makes excel crash. I would then need code to input an event to the sheet next to a date (I have added a textbox to the form to do this). This is my code so far:

Sub BookAPartyButton_click()
BookAParty.Show
Dim i As Integer
Dim w As Worksheet
Set w = Worksheets("Calender")

 With BookAParty.ComboBox1
  i = 3
   If w.Cells(i, 2) = "" Then
       .AddItem w.Cells(i, 1)
       i = i + 1
       
End If
End With
End Sub

Please help!

Maybe:

Sub BookAPartyButton_click()
BookAParty.Show
Dim i As Integer
Dim w As Worksheet
Set w = Worksheets("Calender")

 With BookAParty.ComboBox1
 For i = 3 To w.Range("B1").End(xlDown).row
  
   If w.Cells(i, 2) = "" Then
       .AddItem w.Cells(i, 1)
             
End If: Next i
End With
End Sub

What do you get for the

w.Range("B1").End(xlDown).row

when you single step through??

If it doesn't work that way - maybe:

For i = 3 To w.Cells(Rows.Count, "B").End(xlUp).row

What does it show for

w.Cells(Rows.Count, "B").End(xlUp).row

if it shows the actual last row number then it's not the problem I think it is - why don't you try it with the actual last row number? And, if it works - we'll need to find another way to code for the last row??