In excel VBA, I am looking for VBA code that adds a new line item with the latest month end each time the spreadsheet opens - vba

Question

I currently have a spreadsheet that has individual line items for each month end. Starting in A1, 1/31/2021 and A5, 5/31/2021 for example. My goal is, each month when I open the spreadsheet, a new line item is created for that month; so if it's 5/21/2021 and I open the spreadsheet, it will create a line item with 5/31/2021. Is it possible to include logic that checks the current month I'm in and will open add a line item if it's relevant for the appropriate month?

Answer 1

Screenshot/here refer:
(note - for security reasons, linked sheet above has not VB code - this needs to be built in as described below).
High level
This soln. requires following: 2 named ranges, macro-enabled workbook. Office 365 not necessary.
Setup
Enter any date you wish in column A (max capacity = 100)
Ranges
Create named formula: Formulas | Name Manager | New… set name = 'dates'; enter formula: =$A$1:OFFSET($A$1,COUNTA(1,1000)-1,0,1,1)
(This is a dynamic (automatically grows to accommodate your list of dates in column A)
As for 2) but with following: name : 'Required' (w/ apostrophes), formula = =IFERROR(IF(YEAR(INDEX(dates,MATCH(MONTH(TODAY()),MONTH(dates),0)))=YEAR(TODAY()),0,1),1)
(this creates a formula that checks whether any of the dates in col A already have the current month. i.e. 'Required' = 0 if month already exists (for current year); else 1 returned)
VB
Let the fun begin!
Alt + F11 (open VB for Excel running on Windows)
Locate your file in the Project Explorer (typically default window pane on left hand side; if no such pane, then select from the upper ribbon/menu bar: View | Project Explorer:
Double click the component entitled 'ThisWorkbook' to reveal a new window pane on the right-hand side of the VB window.
The remaining operations appertain to the VB window pane on the Right Hand Side (RHS)...
There are two menu bars with drop-down functionality at the top of the VB-code pane:
Left drop-down / Right drop-down - select respective drop-downs as 'Workbook' and 'Open' respectively, then enter the code per below screenshot (code replicated here for convenience):
Code
Private Sub Workbook_Open()
REQ = Application.Evaluate("Required")
Range("f5").Value = REQ
If REQ = 1 Then
new_date = Format(Date, "dd/mm/yyyy")
Sheets("68516961").Range("dates").Offset(1).Value = new_date
End If
End Sub
Voila! You're all set to go! I tested a couple of times and all appears to be working fine. fyi - don't forget to save as macro-enabled workbook (I prefer .xlsb files as the typically have half the file size compared to .xlsm - the one exception I'm aware of is if there is an SQL connection - in which case it's about the same size as the .xlsm counterpart)...
Functionality:
Every time you open the workbook, the VB code is run - it checks to see if there are any dates that comprise the same month and year as the day your opening the file; if not, the date of 'that day' is automatically populated at the bottom of any existing list of dates in A:A. This gives you the freedom of being able to include other / manually entered dates or otherwise between successive VB created date appended values.
Appendices
Creating named ranges: