How do I call an Excel VBA PERSONAL procedure from a subroutine of another project?

I have a macro that runs via a click on a control button on an Excel worksheet. This macro needs to run a subroutine that is in the XLSTART/Personal.xlsb - (this macro is stable for years and working well via a click on a custom button I've put on the Ribbon).

Now I want to run it from another macro - should be simple enough to write:

                                    Call Re_Set            - there is 1 optional argument that I don't need,

but it just says Sub or Function not defined.

How do I get it to recognise a Personal routine?

[Sorry if this isn't strictly what should be asked here or the Subject isn't phrased well, but you wouldn't believe the time I've spent and the rubbish links I've been given searching 365 documentation etc. with goodness knows how many versions of the subject]

Good grief - I HAVE corrected the highlighted errors, now there are NO highlighted errors.  -  And of course I've submitted more than 2 msgs within 300 seconds - this same msg. after editing!!

Now it says use the Save button - there is no Save button!!!