I'd reduce the Initialize code to:

Sub UserForm_Initialize()
    With Sheets("Bills")
        lbBills.List = .Cells(1).CurrentRegion.Offset(1, 1).SpecialCells(2).Value
   
        sMonth.Value = Sheets("Bills").Range("cMonth").Value
        sYear.Value = Sheets("Bills").Range("cYear").Value
    End With
    
    For j = 1 To Day(DateAdd("m", 1, DateSerial(sYear, sMonth, 1)) - 1)
        Me("dnum" & Weekday(DateSerial(sYear, sMonth, 1)) + j - 1).Caption = j
    Next
End Sub
In design mode you can put the lbBills property columncount to 3 and columnwidth to 72;42;30