Sorry Geoff, I have no idea as to how or what you're doing.

Here's what I did:

Downloaded the file you linked to in post 1, (82.4 MB) to a folder on my hard drive.

Starting with no workbooks open, opened your file (took 62.6 seconds)

hit Alt + F11 to bring up the VBA environment
clicked Insert and selected Module
pasted the macro of post 2 into the module.

Went back to the Spreadsheet.
hit Alt + F8 to bring up the Macro dialogue
Selected the only macro available "LoseThatWeight" and clicked Run.

Things ground away for over a minute then came back to life.

Clicked the X in top right corner to close the workbook
was asked if wanted to make changes to 'chutney-calculator.xlsx
selected save
get a pop-up saying VB project can't be saved in a macro-free workbook...
To continue saving as a macro-free workbook, click Yes
I clicked Yes and Excel saved the workbook and closed it.

Looking in the folder where the workbook was downloaded to its size is now 33 KB and it loads in a second.