How to NewDialog from a spawn dialog?

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When click next button, I want a warnning dialog could show up to give user a choice to confirm his click. If yes, go to next dialog and close these two dialog.
Just like dialog 1 spawn dialop 2, and dialog 2 could go to dialog 3 straightly. However, if I dialog 1 spawn dialop 2, and dialog 2 "NewDialog" dialog 3, it will go error. So, how to realize this effect？