How do I code (VBA) fixed date entry upon opening workbook?

Hello,

Firstly, apologies - I am completely new to this so please forgive possible stupidity!

I am using an Invoice Template in Excel 2007 and would like to know how to code it so, when I open the Template, the current date is automatically entered. However, I do not want to use

=Today()

or

=Now()

as this updates whenever the workbook is subsequently opened, say, a week later. I also do not wish to use the "Ctrl" and ";" to hardcode it, as I shall be giving this Template to another person for the actual invoicing and am looking to have as much of this automated as possible.

For reference, the WorkBook is called "Invoice_A4_Template.xls", the WorkSheet is named "Invoice" and the cell reference is "I4".

Apologies as I realise some threads on this have been created, and I have genuinely tried reading/understanding them, but I'm still struggling so thought I'd ask personally.

Many thanks for taking the time to read this thread.