I am trying to workout if its possible to have a MsgBox pop up when the spreadsheet opens, I know that can be done, but I am trying to get it to tell me this...

Column A I have a list of Engineers
Column B I have an expiry date for his Works Certificate.

I want to try and have my MsgBox pop up on Open and tell me that Engineer X has an Out of Date Certificate. I am trying to get it to do this a month earlier than the date, and give the user the option to change it now or cancel for later, I then am trying to have the same MsgBox if the user cancels it everytime the user opens the spreadsheet till thedate is changed.

How is this possible to do?

Go into your VBA project for that workbook and open the workbook code. Use this sub:

Private Sub Workbook_Open()

'Code for workbook_Open

End Sub

Hope this helps