You can export (save as) a schedule to an XLS file but I don't think you can import I file into an interactive schedule.
The IS links to elements in Archicad and has no calculation abilities (except sum).
External spread sheets don't link to anything in Archicad and can do all sorts of calculations.
So the two are not compatible
You can place a PDF of your spread sheet (with the drawing tool) in Archicad and it will update when you re-save the PDF.
That is all I can think of.
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