UDF .Volatile results to #Value! error

I got this code (from somewhere, maybe here) that returns the items selected on a pivot filter.

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UDF works fine, it recalculates when I change the filter and when I refresh the pivot BUT I also have a macro initiated by a button that refreshes the pivot (pivot is somewhat hidden, that is why I need the button). The macro is simply:

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SO, when I refresh the pivot via the button i get a #Value! error. If I reculc (full or F2 enter on one of the cells containing the UDF) it works fine again.
Can anyone please explain, resolve?

maybe

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thanks guys will try monday (other project got in the way)