I've created an add-in with functions, subs and an "auto_open" function that
loads a custom menu. I'm looking for a little guidance on what path to take
to accomplish the following:

My user opens a monthly spreadsheet with data to be transferred to access. I
only want my add-in to load and subs, menus, etc. to work in excel if this
workbook is opened. This spreadsheet is machine outputed so I will never be
able to have vba code inside it. I also don't have a lot of control over
it's file name. I could detect if it's the right workbook based on certain
cell criteria though.

Should I add my add-in permently to the personal.xls file so it's always
loaded and have "auto_open" check for cell's meeting my criteria and then
let my custom menus appear?