The style sheet must be within the project but with that
proviso, you can use a style sheet coded outside RH. Indeed, I
always make a point of editing my style sheets externally rather
than let RH put in a load of unnecessary code.
The only problem is that sometimes such spreadsheets contain
some coding which causes problems, usually when it comes to
creating printed documentation.
I would say backup and then try it out. With no guarantees, I
doubt it would crash RH or corrupt it. The worst I would expect
would be the wrong appearance or some hiccups.
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