Add custom cell formats to all spreadsheets

[hip2b2]

I have a number of custom cell formats that I would like to have available whenever I create a spreadsheet (it would be even better if I could use these on old spreadsheets but I don't think that is possible).

I have found that if I modify (add the custom formats) and save "book1.xltm" template located in "C:\Users\username\Documents\Custom Office Templates" with the custom formats I can open this as a personal file, but I'd like this to be the universal default for all spreadsheets I start on my computer.

Is this possible?